Here's what i found so far as an amateur.
I have SK 10Y with rear speakers (SPK8-S). I sit 8-10 feet away from my soundbar and have 9-11 feet ceilings. I arranged my rear speakers 3 feet back from my sitting position. Placed sub woofer next to soundbar with Apple TV 4K and have 48" samsung 4K TV.
After going through some settings with multiple movies with Atmos and regular 5.1 HD/4K movies here's what i found and worked best for me.
similar settings were also mentioned by paul douglas in previous replies.
Standard mode picks up low sounds better than any other mode (as others mentioned in this thread)
sound mode: standard
Surround: On (hold Auto Vol button on your remote for 4-5 seconds to activate the setting and push again to switch on/off surround)
Sub woofer: 0-1
Center: +5 (audio is low in Atmos, you can crank it up to 6)
If you are watching news (CBS, CNN, Reuters etc), generally these are not multi channel. I prefer to switch the surround setting off for news)
I liked bass blast and ASC modes for music and Music mode didn't impress me much.
If your streaming app or box provides multichannel audio, use standard mode with surround on. Normally live events are not multi channeled so i use standard mode with surround off and center speaker +3-4 (commentary voice gets loud sometimes )
If you are watching most movies thru netflix, you need a Ultra HD subscription to activate Dolby Atmos
. You need a very good HDMI cable to pass high quality audio (i am using Atevon High Speed 18gbps 4K HDR HDMI cable bought in amazon)
Here are some movies and TV series with Dolby Atmos in Netflix.
Bule Planet II
LOST in Space
Guardians of Galaxy Vol 2
Punisher (best i have heard in this list, especially when he uses hammer in the construction building. You can literally feel the rubble)
Altered carbon (also good atmos)
for more type Dolby Atmos in search bar. you will find more titles
I really liked the setup and it does not compare to individual speakers system (7.1) my friend has in his basement but impresses an ordinary user like me.
This review is my personal opinion only, some of the professionals in this group probably have a better advice and settings than i do.
Anyway... Have fun with your LG SK10Y