Modular Room-w/in-a Room HT? Think's a good idea?

Soix, since sound isolation (keep in and out) was the main goal in the room, I failed in number of areas, yes. First was (for just bare min acceptable results imo) NOT USING RESILIENT CHANNEL N ACCOUSTICAL ISSOLATION CLIPS!, yes. While I considered this, I tried to save max inner room dimensions in small room (was,11.75' x 13.5' x 9' originally), n opted to only FURRED OUT the walks w staggered studs -even in closet -to isolate from outter walls. I would say this had only minimal effect ultimately in the upstairs spare bedroom flanked by other bedrooms. Then I simply 1\2" dryall + green glue + 1\2" drywall inside (tried keep it thinner because it makes sound HARD n unyielding inside, plus not enough base absorption., so counter productive in noise isolation). Then I used sound cover over windows to help there (again minimal effect)
Next failed effort was FLOATING FLOOR CONSTRUCTION! I didn't engineer it correctly, partially in attempt to keep floor thickness to minimum yet "floating". I used 1\4" foam closed cell pading underlay, with Hardybacker board heavy underpayment + green glue + lamin flooring over that. This also only minimally helped, but mostly hardly at all!!
What should been done is perhaps small modestly spaced acoustic isolation rubber pads with sound deadened sandwiched 3\4" plywood construction, I believe. Really the minimal isolation point contact between subfloor is key plus mass floating above it as new floor. . then prob carpet n padding.
Next was hard dropped ceiling which WAS NOT USING RESILIENT CHANNEL, NOR SPRUNG WITH ACOUSTIC ISSOLATION SORINGS. Either way that also needed to be isolated, and it ended up not being done!! So also dropped ball there, partially from compromised soffit design recommendations from contracted construction guy and wife's desire for inceiling lighting choices. I caved in n failed basically, sound issol wise.
Of all things, probably the solid door and new jam helped plus sealed weatherstripping rubber around, and seal at bottom had best results compared to otpriginal hollow crap door.
All in all, ideally some floating floor with separate isolated room - within a - room concept would have been way better (including improved bass ISSOLATION with added wall spacing depth, but left small small space inside ultimately. Second best - and only real viable improvement option for space, budget, and practical application was to probably still fur out wall to isolate walls between rooms, THEN PUT SOUND CLIPS N REZILLIENT CHANNEL + sandwiched green glue construct drywall attached to that all around the room! (Including over newly built soffit +acoustically sealed recessed lighting or other lighting option externally)
Also I'm sure some sort of isolated doubled thick pane window configuration or thick cover or something to help sound there.
Anyway, yeah, made mistakes and you really can't when it comes to sound issolation !! Sound doesn't know you are trying to keep it in or out just because you TRIED!!! LOL.
Next time I'll put a better effort forward, for sure

Keep in mind I am aware that even simplly isolating w RESILLIENT won't help keep bass in or out very effectively! Only wall thickness depth and mixed with mass barier is only way there. SPRUNG walls only really help mid and high frequencies used with green glue or deadened drywall.
In this respect, the separate issokated room-in-room (possibly with heavy dense ouuter wall shell barier??? ) would get best bass isolation effect by also spacing outter vs inner wall structures, im sure.
Just more thoughts there.

I suggest you check the Quietrock website.

Ptss, ...I wouldn't waste my time again. This is merely another drywall product with patch and calk! 100% sure if I switched out my green glue sandwiched drywalled and sealed/calked walls in the room with Quietrock, I'd have zero improvement in results, basically ...and likely worse.
Um, yep...channels, separate walls, room-within-room, etc...only ways. But you let us know if it works out for you, of course.

"Keep in mind I am aware that even simplly isolating w RESILLIENT won't help keep bass in or out very effectively! Only wall thickness depth and mixed with mass barier is only way there. SPRUNG walls only really help mid and high frequencies used with green glue or deadened drywall."

Ooh. That strikes me as exactly backwards. Resilient channels are helpful in absorbing low frequency bass waves and preventing them from being transmitted to the studs and then to the rest of the house with the added benefit of improving the bass characteristics within the room itself. Trying to do that with wall thickness would require walls way too thick to be practical. Obviously constructing a room within a room would go even further in improving isolation. On the flip side, wall thickness/damping can be very effective in preventing the transfer of mids/highs while also helping acoustically in that range within the room. If you haven't already, get Premium Home Theater by Earl Geddes. Haven't read it in a while but I think I got this right. By far the best book I've read on how to construct a dedicated room, and it applies just as much for audio as it does for home theater. Highly recommended for anyone looking to build/treat their listening room.