Super weird question about G-code & differences between machine architectures!

Hello! I am just going to post this here since y'all would probably know!

Is G-code unitless? or if it does use units would it be able to work with nanometers or would it run into issues?

Also I've only ever seen 3d printer architectures where the plate moves in x or xy, is there any filament (not resin) where the plate moves up and down instead? (or any other weird architectures!)