Just an idea, but you could just use the physics as you’ve done so far.
You could make a sphere (or some mesh that could deform it) and add a collider to it.
You could make it go with the pillows and see if they deform.
If this is for a render, you can simply hide the sphere or bake the rigidbody world… or simply apply the cloth modifier.
Idk there’s a bajilllion ways to go about it ;-;
unfortunately, I still have yet to uncover the solution towards the conforming issues. All I did was try my best to place the pillow just above another without using snapping tool.
Its pretty good , only issue I noticed it the middle cushion thing has no curve to the surface like the pic you showed, also I guess that whole middle section is very sharp but it would be more like the end pieces