Lewi
there is a way to change resolution in dolphin, but it is not very user-friendly. In Batocera ES press F1 on a connected keyboard, then navigate to Applications and start dolphin-emu-config. There you can change resolution. Then when you want to start a game, open it via the dolphin-emu menu (in the upper left corner go to Open and then navigate to /userdata/roms/gamecube (or wii) and select the game you want to play )