Is there a reason why the database for the MegaDrive games often only includes the European variants of games? I think using NTSC versions might solve the issue of sound being too fast in some games (for example, Power Rangers The Movie).
I think the emulator is playing all the games at 60fps and the European ones should bde playing at 50, if I'm not wrong, because it looks to me that's the entire game that is running too fast and not just the audio.
You can still play the US version of most games