I don’t think many have used a joystick with the MPCNC other than a few that use estlcam firmware. Some use octopi to touchscreen from there phones. It really is much easier to just move it by hand, it does not have the limitations of giant machines in this way.
If you use the dual endstop firmware you can not manually jog it work offsets are the way to do it.
Maybe it would be better for the Lowrider but same deal it only takes me a minute to jog it into position.
Never used a touch screen, if it is a reprap screen it should work with any board no issues other than the LCD adapter for the Rambo. I have not used a touch screen though. I am kind of old school about the screens though, sometimes experimenting just gets in the way of getting work done for me.
Can’t wait to see what others say.
I highly doubt you will be able to get a mach3 control to work with Marlin though.