Update – when switching to mame4all as the default emulator (non-libretro core,) the resolution issues are fixed, but the joystick config isn’t being honored (not usable at all) so I will be digging on how to add the joystick config to the standard mame4all cfg file.

I really liked the nice, neat cfg setup with the lib core, so I would still be interested in hearing a solution to the issue.