And I am not sure if you know that is ,launcher also supports custom config for every type of Emulator by put a retroarch-local.cfg into /home/cpi/apps/launcher/Menu/GameShell/20_Retro\ Games/[MGBA,MAME,etc...]
The Settings->Buttons Layout and press the key for “UpdateRetroArch” sets up the proper Key Bindings for your layout. You would probably want to go in a tweak your settings for your personal preferences afterward.
Just so you know, the option that was making your screens small is “Integer scale”. That makes the resolution only scale if it’s 2x, 3x, etc… Entire/full/integer numbers (not 1.8 or 2.243)! It must be set to off so that it will scale even if it doesn’t reach an integer.