Piano Practice Studio

Hello after several days researching this site and others I came to the realization that I need specific recommendations and this forum looks like the best place to get it. Of course I will make a little donation for the help! :D Project (planning stage): Piano practice and Hi-Fi listening room “man cave” to be built attached to back of townhouse. Goals: A) Sound insulation for neighbors and interior of house (lesser importance) B) Acoustic quality for Piano #1 & #2 Hi-FI. (I will address this on the correct forum thread if necessary) Sound level: General 60-70db, peak 80db. Classical music practice and listening. Magnepan speakers/with sub & 7’ Grand Piano. Construction dimensions (ID): 11’.6”x17’ x 12’-11’ graded ceiling lengthwise. Constructions Materials Available: Similar to what can be found in California. Proposed Construction: Floor: 4” concrete slab, PE sheeting/ Cork Flooring (hardness rating 830) Walls: 2x4” 20GA steel, 16” spaced; RS1 Channel 24”; 2 x5/8” type X DW with Green glue (1 tube x 4x8 sheet) ; R11 Pink Fiberglass. Perimeter sealed with Henkel. Exterior: 5/8” Densglass sheathing, stucco, sealed, paint. Ceiling: 2x6” 20GA/ 2x 5/8” DW; Hat Channel; R19 Pink Fiberglass; EPS Crown molding Perimeter sealed with Henkel. Roof: 3/4” plywood, Roof sealant layer, concrete shingle. Perimeter sealed with Silka Sealant. Windows: 48”x48” (need suggestions on materials) HVAC: Mini-Split After a lot of research I think I’ve come up with a descent build but would like some feedback from the experienced. My main concerns are the windows but I need some natural light so I would appreciate some suggestions. I am not that concerned with sound entering the house through an exterior insulated build French slider. Moving the piano into room will be a huge difference for and give me the privacy to practice in peace. Questions: 1. Recommended window materials 2. When hanging the 2nd sheet of DW is it important to have the bottom ¼” off the floor then sealed with a slab floor? 3. R11 or R13? Acoustical difference or just thermal? 4. How to maximize acoustics for the Piano from the players perspective and the Hi-Fi system. Piano Positioning, Bass traps , acoustic panels ( currently have 4 each 24”x48” and 2 24”x24” panels) 5. Any special considerations for installing the minisplit? I will need to punch a about a 2” hole through the exterior wall. Thanks in advanced