Those that don't know history are doomed to repeat it.
Time to go back into the history of cinema, to the beginning about 90 years ago. Back then, going to the cinema was what the uber rich did as they had air conditioning, tables, food, drink and cigar venders to keep the party going. The movie moguls were deeply concerned to give the best presentation so cost was not an object. They ran the new "talkies" with massive Western Electric horn systems to provide the sound in glorious mono! Oddly enough, those huge screens with the mono speaker in the center gave them headaches which is not a good thing when mob money was involved so they did a study on why a person had headaches from watching movies on the big screen in mono.
Answer? Because the sound did not follow the action on the screen and the eyes had a dissagreement with the ears or a conflict of senses which creates a "fight or flight" response causing listening fatigue. Their solution was 3 channel, the sound would track the movement on the screen to eliminate sensory conflict and all was well. Frank Sinatra had a sound system in the late 40's/early 50's that was a 3 channel complete with the manditory 3-channel tape machines to support his expensive habit. Granted, for the lowly masses--3 channel was not a thing because of the huge cost of tape media and the machines but 2 channel could be made cheap on a record. The downside was you had to follow the rules of 2 channel and sit between the channels to get the illusion. It was noted if you sat 10 feet back, you should space the speakers about 10 feet wide and toe them in properly and done. Sure, it only "worked" for one or two people in the center but it did work with records for the time.
The concept of "home theater" is to mimic actual movie theaters and there are rules that must be followed. Visit a movie theater, look behind the screen and note where the speakers are located (3 for smaller screens and 5 for larger screens) Notice where the surrounds are, how many of them there are and where the Atmos speakers are located. This is a HUGE expense so ponder that for a bit--you will never see Atmos reflecting off the ceiling or the screen speakers pushed together--at least not now with the technology available. If those million dollar plus cinemas can't pack a pile of speakers in the center of the screen and make it work with their budget--how would it work at home?
Other factors that apply to speakers etc. also apply to soundbars. Basically, it is called "Hoffman's Iron Law" laid out in 1957 and it still applies. Loud (efficient) Low (bass bandwidth) or Little--pick two and lose the third. If you go to the extreme on the small size, you lose efficiency and bass response--nothing personal, just math. Easy to wrap your head around, a boombox is neither loud or able to go deep in bass response because of size/weight/power constraints and neither are smart speakers, clock radios or cell phones. The world would beat a path to your door if it could! You can't get beer keg performance out of a beer can, such is life.
So you want a soundbar, what would give you the best performance? Well, go back to the original 3 channel rules that made their debut in 1934--get one that is as wide as the screen to prevent visual and sound conflict. As the TV gets wider, the soundbar should get wider so it places the left/right speakers to the edges of the TV. Think back to boomboxes, the all in one blocks did not sound as good in stereo as did the boomboxes that had detachable speakers--the same applies. Go as wide as you possibly can to get the left/center/right information correct and do that FIRST! Don't shoot the messenger, blame the movies companies for that one. IF you use a very narrow soundbar on a big screen, you will have issues with sound tracking on the screen which leads to listening fatigue. It does not matter what the speaker quality is, if it don't track the image on the screen you have failed. Sure, marketing claims ways to "widen" the image and even boomboxes had "stereo wide" many decades ago and it did something...but in reality it was best to do it right and get detachable speakers for proper placement.
Soundbars were not invented to be a single home theater in a box. They were specifically designed to be a multi-channel boombox, much better sound quality than tiny little TV speakers on flat panel TVs. Back when they came out 15 years ago or so, TV screens were 40 inches or less so they worked fine because they "matched" the width of the TV. Over time, the width of the TVs became larger which creates problems for soundbars because they to must increase their size to "match". The cost of that would be huge as you need one for 43 inch TVs, 55, 65, 75 or 85 inch TVs and that creates problems for cost, complexity and what the consumer is willing to pay.
In your case, there is no soundbar that would "match" a projection screen. The reason for this is obvious, no demand for such a thing and the cost/weight would be very high. Personally, I have never heard of a person putting a soundbar behind a large projection screen because a screen is a perfect place to place speakers behind to "hide" them--one of the big attractions of projection screens right at the start! Most people that have projection screens have no problems with the "complexity" of putting three speakers behind it because using a projection screen and a projector is a much larger hassle in the first place.
The "solution" would demand a soundbar that has detachable left/right speakers so you can match the speakers to the width of the screen. Much like the concept of detachable speakers on boomboxes--get a soundbar that has detachable speakers to place them at the edges. I have no idea if such a thing exists (yet) and it won't exist until there are enough people to purchase such a thing to make a profit. At this point, soundbars are marketed and built to be small, fit under a TV and give decent sound quality with those severe constraints--Hoffman and his silly law has not been violated.
Atmos... in theaters they place the speakers where they want the sound and done. As far as bouncing the sound off the ceiling and reflecting to your ears--that goes back to 1969 with the Bose 901. That trick over 50 years ago sure made the speakers sound "big" and the marketing proclaimed it was nirvana--plenty of people were hooked on the Bose sound and the world stood back in amazement. Well, it was interesting at the time but it was not accurate and created massive problems considering the room, the placement and even the type of walls it was reflecting from created all sorts of issues. It did sound big, it did sound different but in the end it was not accurate and went away. Bouncing Atmos off the ceiling is along the same lines, it does "something" and does sound "bigger" but you have multiple problems because your ceiling is not flat, your ceiling is not "known" for frequency response with the reflected sound and expecting a tiny speaker to have the SPL to go the distance to the ceiling, reflect which absorbs sound then make it to your ears demands a much higher SPL capability than the main speakers. Don't blame me, just simple science, math and how sound works. At best, you would get "something" of an illusion but only at low SPL and never mind if the Atmos speakers are built in they have to fire through a screen (screen does reflect and absorb sound) it has to hit the ceiling that has angles (not recommended) then make it to your ears.
Think about this logically, if you won't get the left/center/right speakers correct so the sound tracks movement on the screen, how can bouncing sound off a ceiling create any real illusion since the front soundstage is not correct at the start? It will do "something" just like stereo wide on a boombox does "something" but it will in no way be accurate, the movies are not mixed to work with that arrangement and your ceiling is not correct for bouncing sound?
Now you want great music quality? Geez, demand much? I would love to have a boombox that had enough power to be used as a PA for a small bar gig also... the downside with that idea is I could not pick the beast up! Assuming you are listening to two channel stereo, the RULES still apply for proper speaker setup. If you listen back at 10 try to get the speaker seperation 10 feet back--toe them in to limit wall reflections and get the on axis frequency response to dominate what you hear. I have not seen a 10 foot wide soundbar--well, there is one that is 8 feet wide made by a master woodworker that used three 8" coaxials and premium woods. He listens to it 8 feet back and it is powered by an AVR with the subwoofers blowing through wall vents as the subs are mounted behind the wall in the garage--it is possible but it must be custom built. Engineers sure make some cool toys but it worked wonderfully.
Maybe in the future technology will allow sound to appear where the speakers are not located, line arrays can "steer" sound but the tech is not available yet for multi-channel all-in-one boxes. In your case, the most extreme of a giant projection screen the LAST thing I would do is use a soundbar! It is not the soundbar's "fault", they were never designed to do that in the first place. I'm not a soundbar "hater", they work well and I have spec'd and set up a few of them for family and friends. A great solution as long as you know the limitations going in. Just as my smart speaker will not give me high fidelity, it can't no matter how much money I throw at it. A soundbar can't accurately mimic a movie theater because it can't no matter how much money you throw at it. An all in one boombox can't mimic a proper 2 channel stereo because the speakers can't detach. No problem, most people know the limitations going in and if the solution works in with those limitations then go for it.
Since you have unlimited funds but very limited time or technical knowledge--you can hire people from a theater place to evaluate, install and wire everything up to get the best sound quality within the constraints of your room. In wall speakers, onwall speakers, acoustic screens, wireless surrounds and the entire system can vanish without taking up much space. It will cost you some cash but at least you will get what you want. I am assuming you have a screen that allows sound to pass through, if not get one that does. I would hide the three speakers behind the screen (6 speaker wires) and you can get wireless rear surrounds by using studio speakers for whatever level of sound quality you desire. Atmos? Well, it can also be "wireless" but you need to provide power outlets in your ceiling--that depends on how far you want to go. Putting power outlets in the ceiling will cost some bucks but you don't seem to be worried about cost.
In summation, a soundbar does what it does but it can't give realistic sound with a 150 inch screen! If you want 2 channel music, you have to follow those rules to get it to work properly. Atmos? Follow those rules and so on. I would love it if a soundbar could do that, the movies theaters around the world would be switching rapidly if it worked! You can bet those touring bands would love to throw a giant soundbar on the stage and be done with it. I really, really, REALLY wish it would work as I'd buy one! However, it does not so respect what it can do and be aware of their limits no matter how much money you throw at it. Maybe in the future that will change but I am not holding my breath for a King Kong sized soundbar becoming available to be spaced properly for 150 inch screens.
You can get one designed and built to do that, millions of people around the world have built speakers to custom spec be they for theaters, pro sound, touring sound, automotive sound or for people that want high SPL from 5 watt tube amps--you can have custom speakers built to your specific needs but it will cost you! Just points to ponder, sound does what it does and you have to play by it's rules... Realistically, a projection screen is far beyond what soundbars are designed to do so look at solutions for projection screen sound. Good luck.