Emulator crashes on the Pi5 (which is still pending support) are usually caused by the 16K page kernel used by default in RaspiOS. TL;DR: modify /boot/firmware/config.txt and add kernel=kernel8.img at the end.
If you wish to run the standalone emulator, you can modify the controller bindings by starting the GUI and using its configuratoin menus. Install the desktop, then start it and then execute /opt/retropie/emulators/dolphin/bin/dolphin-emu to get the emulator's GUI/menus.