I'm probably going to run Marlin just because it would be the first 3D printer I've actually made and I've heard it's more beginner friendly. I think Klipper also needs a dedicated host like a Pi which is a bit more overheard I don't want to worry about, but I'm open to exploring any type of firmware!

Very cool, keep it up and I'm really curious if you manage to drive a printer with it and what kind of functionality you're going to achieve. Keep an eye on things like accelerometers and filament runout sensors in the toolhead, those are becoming more and more complex.