Yes, you only need AutoRCM if updating ofw, so emuNAND is safe, but you can't use game cards after updating in ofw, because it has a different firmware and it's fuses will burn, and you will get an error when booting to ofw with a game card inside, so take it out if you want to boot to ofw, but I never heard if it saves those fuses if you do enable AutoRCM, so you can try and reply to that question, I myself can't because my game card fuses burned on 9.0.0 emuNAND when I didn't know it would happen even if you don't put a game card inside the slot on emuNAND, like it was on lower firmwares, and my ofw is on 5.1.0, but if your ofw is on 9.0.0 or higher your game card slot will work, so no AutoRCM needed, so I think.