I never experienced the problems you are mentioning and feel like, Windows 10 would be less reliable and slower on a raspberry pi4 than raspbian.
Did you make sure to follow every single step in my guide? Did you start with a clean raspberry installation?
Joy sticks are at the moment not supported due to directX not being supported on raspberry.
Please refer to Mission Planner on Raspberry Pi 4, no Luck for further help.
Cheers
Edit: surely, mission planner on a raspberry is not quite as fast as it could or should be on a 64bit system. However, we haven’t found a promising solution for this. It’s by no means unusable however.