You can change scaling in options gear > user interface > appearance > menu scale factor

If you’re only interested in a few consoles you could try dedicated emulators.

If retroarch is too much you can try Lemuroid. Lemuroid is a much simpler emulation app with a more straightforward GUI. It doesn’t come anywhere near the features or number of cores of retroarch but it supports most common retro systems.

Mypizzaboy is the best android emulator tbh

I don’t know how it works in RetroArch, with Delta/Ignited you can change the skin which also manages the size and position of the screens. I even designed custom skins to play full screen with no controls with Zelda since you don’t need the abxy and arrow buttons to play.