1room studio in cellar

Hi everyone, I´m Jürgen and I live in germany. That’s the reason for my bad English. In the moment I´m building my own house and in the cellar will be one room for my small studio. I will create the studio in the next days. In the rear I planned one separate room for the heating system and one for a vocal-booth. Does it make sense to build the walls in the front as you can see it on my sketchup? The front- walls have to stand in this position because of the window-length. The monitors are standing on the table (behind the Mixing console). I would like to record mostly voice and guitar but not for professional use. So it should not be to expensive (maybe500-1000$). After creating the room like that (if you support my ideas) I will do measurements for standing waves and room-reverberation or Is it possible to estimate which kind of diffuser, bass tabs or absorber I need in this dimension? How much room-surface do I need to record drums? Maybe I make the vocal-booth a little bit bigger, so I can also record drums there. I thank you for every information, Jürgen