@mitu I'm stupid. Somehow turbo mode was on and that's why there was no sound.
Sideloading the built-in SDL library doesn't help. But I'll set the export thing in the redream script. The underruns don't seem to affect the gameplay otherwise...
Anyway thanks for the help! Another little quirk is gone from my list. :D
I don't know much about two player, but try pulling the plug, then plugging it back in without controllers. You'll get to the configure screen. Configure your second controller if it is unconfigured then press any button on your player 1 controller to get to Emulation Station. I don't know but theoretically it should work fine.
FIX: After looking around, I found es_settings.cfg and saw that "Sort All Systems" was 'True'... Changed value to "False" and it was sorted the way I prefer and edited! :)