NixOS is exactly what you want.

You declare your configs in a way that you can just copy them to another computer and it willbe configured the same way.

I’ve never tried it my self, but I might for my next machine.

This is the real answer

Will I be able to do exposure stacking with the overlay module?

I believe you are fixating on something that won’t have much impact regardless of what choice you make. I have been using “windows keyboards” on Linux for years with literally no problems (related to keyboards and Linux). I mostly game, browse the web and work as a software engineer.

Focus on what feels good physically/ergonomically for you and your workflow and you’ll be golden.

The only caveat I’d throw in there is if your keyboard of choice has some sort of RGB program for Windows or other custom software. It might not be as simple to control that functionality from Linux, but in many cases there are open source Linux alternatives for that software.