room in room or just a second wall uncoupled?

Hello, at first, sorry for my bad english, hope everybody understand what i mean. So i have an old cooling chamber of an old german beer company. There are very strong stone walls. 50 cm in the door space and i think that all walls around are so strong too. I want to build there my project studio (low budget but the best i can). The room is 6,7m x 5,8m and 3m high. I plan to have one control room, a little drum room and one little vocal / amp booth. (so i am able to record a whole band at once) (As you can see in my little plan, how i image to have my control room.. i think about soffit mounting my yamaha hs80m, to get more space in the control room) I think that i don't have a problem with the loudness outside, but i need to build strong walls between the control room and the two booths. Till today i was sure to build room in room with 5-10 cm space between the strong stone walls and double walls (each 12cm strong, wood walls with rockwool inside ) with although 10 cm space between the 3 rooms. But now i think if its really necessary to build room in room. Its better to build the walls uncoupled from the stone walls, the bottom and ceiling? What do you think, or what do you although need to know to give me your opinion? My next problem will be the air condition because there is only the door and one whole (30x30cm) in the wall, but that is the step to plan after the walls. :-) Thanks for your help.

if you don't need a room-within-a-room for the CR or vox booth, then make the drum room basically a large isolation booth. for the AC, use split unit AC in the CR and baffle boxes on the side of the vox and drum booths to exchange air with the CR while ensuring isolation.