Garage interior finish

[ryans69chevy]

Just wondering what thickness of plywood I should finish off my walls and ceiling with in my detached garage. It's 24'x32' with 8' walls with a 20'x15' and 10' walls on the back. It looks stupid I'm not sure why someone did it like that. I'm fixing everything up so it's nicer in there. Rotting wood on the bottom plate and such. Also I'm making the ceiling 2' on center. Going to insulate the ceiling with R-19 and then the walls with R-13 or possibly R-11. I'm going to plywood cuz it's my garage and I want more durability. And also I'm not gonna heat it fully all winter just when I wanna go out there and work. Or else have it at a certain temp just to keep the bite away. But since I'm doing that I don't want rock since over time the mud will start cracking... So I'm gonna do BC plywood. I'm thinking 3/8" on walls and ceiling. I'm not sure if that's too much or not enough. What are your guys take on the thickness??

Thanks,
Ryan