Spring-loaded sound-deadening drywall screws.

I saw that a few days ago, looks promising but the price will need to be competitive. It would save about 1 to 1 1/4 inch per surface of walls and ceiling compared to clips and channel. I also thought about two layers of DW. From the picture it looks like it is designed for a single layer. I wonder if there is a work around of using laminating screws for the second layer making sure you don't hit a stud.

How does a vertical side wall attach / seal to a horizontal ceiling wall if they can both move a tiny bit?

flexible caulk just like ceilings and walls on clips and channel.

I saw that earlier too. I bet someone will try to use them in ADDITION to DD/GG/clips/channel/etc. when they become available. Or at least the question of doing that will be asked a million times here. 😜