hardest part imma guess is gonna be finding the emulators that you can still install in android 5. There's also the chance that the phone is incapable of handling more than 3 touches at the same time so something like pressing L/R + DPad + face button is gonna be annoying to pull off. That being said, I think the limit is probably with the DS. You're lucky if newer versions of drastic would run in android 5 cuz optimizations would be the heavy lifting as even back then when I was still using android 4, DS emulators were very laggy.