Pretty much everything is the same. As for the res thats up to you, you can play native res or up the res. But you defo want to up the res on some of them older handheld games and even PS2/GC/Wii etc as it makes a huge difference and makes the games feel like remasters.
Is the resolution based on the rom I install or handled by the emulator settings?
Apologies if these questions are basic, but this is all new to me.