Hi @yellowelise are you planning on designing your own firmware? of course, when you flash your m5 device with our burner software it is flashing a .bin file a .spiffs file and a few other files, you can also do this by command line if you choose with esptool. It would be good for you to expand on your questions more so we can better help you.
iIRC I seam to remember something on one of the Esp32 forums with a similar issue. I think it was something to do with bus clock speed issue. I think it was down to the clock being set to high for the psram.
It's all a matter of taste I guess. Three buttons just aren't that many, I prefer to use as few keypresses as possible. Nobody is going to write their thesis on it: it's for WLAN passwords and the like.