My plan is to build walls around the structure and use the roof. Currently it's an 20x20 space with 4 metal poles and a slanted roof. Sound isolation is priority as i'll be mixing and recording music late into the night. The loudest things I'll be using are a pair of 12 inch monitors for rehearsal and low wattage (5-20) with single 12 inch drivers. No drums unless it's daytime which won't matter as much.
I'd like to maximize space so ideally not building a room within a room. It would be nice to minimize costs of course

Should I build staggered walls? Or can I just build standard walls?
I would love any advice and have already have cost estimate and a contractor to do the work and currently the plan is just to build the frame and leave the interior bare just so I can get started. I have a few pictures added below
Please let me know if I missed anything!
Hopefully this is a good amount of info to get started and look forward to your suggestions and thoughts!
Aloha from Hawaii