Wow! My front wall is 16’ wide and according to my measurement a 200” screen would basically take the entire wall. My seating distance is at 16’, and room is 24’ long. I can not imagine watching on a screen that big. I think 150” would be it. For me anyway.
I also have a studio in my house that’s built with acoustic Sheetrock channel, and fiberglass batting in the cavity. Doesn’t seem like it does very much, especially drums. So I think you’re room in a room is a good idea if you’re concerned with leaking sound. The staggered stud concept seems to work well and not intrude into the space much. Also, seaton sound is a great investment. Mark is a brainiac and a super nice guy.
Also agree, 7.2.4 or 7.4.4 would be a great investment. If you’re budgeting high enough, and doing multiple rows, 7.4.6 might be worth considering too. The added height speakers can help with more seamless playback although processors are very expensive, and 4 top speakers can create really good phantom imaging and smooth pans too. If they have wide dispersion. FWIW my space is a LR setup and is 7.3.4. Imo, it’s worth it. Even on legacy tracks, DSU and dtsNX can create awesome experiences. Hope that offers something.