Yes read up on what happens in a room. And take your time. Acoustics is complicated but, understanding the fundamentals will help you thru the jungle of jargon you’re going to encounter if you go far with this.
As mentioned, drums require space to sound like you think they should. And your space will be a problem if you want that spacious sound.
I am new to the process myself and I found it very interesting that you want a particular
balance of absorption and diffusion. Absorption to remove flutter echoes. If the room is bare, clap your hand and notice those short reflections that I think sound like you’re in a pipe. Those are the flutters and you can reduce them with absorption panels made of rigid insulation and other materials like drapes. But too much of that takes away the spaciousness of the room and it sounds dead.
Low frequency control is very difficult, at frequencies below 200 Hz.
The ideal place for monitors is so they project down the longest wall in the room. So if you use the 10 x 12 room they would be backed up against the 10 foot wall.
You can get good sounds from your drums with close micing and blend in the OHs for ambience. I know your kit sounds great already.
For the long haul and your future plans, get a copy of the book The Master Handbook of Acoustics. Chapter 13 goes into detail about how sounds react in a small room; where the standing waves occur and a whole lot more.
Get the program Room EQ Wizard (REW ) and actually measure the room response. There are people willing to take those measurements and give you sound advice.