It's a very good question. I have seen some pictures of surround systems in very small apartments and I have read some articles.
My experience having both they are different, I think your listening space should engulf the size of room. If I had a 20' X 30' X 12'ceilings I don't think I would lay out a 5' X 5' niche in the corner. However when I was building my surround for car I did do a layout pretending equipment and wires where as if in the car.
The home 12' X 14' with 8' ceilings has a flavor for lack of a better word, that has been played and tweaked to my liking. I think it sounds bad ass. I am basically the only one that has listened to it, my biggest fear in life is a group of QQers would come over and say this sounds like shit. It is hard when you are your only feedback.
The car, I used a Crutchfield mounted Blu Ray player, USB in- sub in trunk-3 mains on dash, 2 rear deck-and two mids front doors, the key is the JBL DSP that you access from Ipad, and you can really dial it in, plus all the auto deadening stuff. I have never played an Atmos file, I just keep with 4.0's and 5.1's.
The music is exaggerated when I say in your face, like if there is a swirl going round in speakers, or an isolated voice coming from rear left, man, you really hear it,
Keep in mind it is not a small niche in house it is a vault of plastic metal and glass, where sound is mostly not escaping, the DSP on the Ipad is really important.