I currently do not have a working build enviroment due to a recent reinstall so this is something that really only applies to IQ:
I have spent some time looking at the megadrive driver in the past. The only trouble is I now have 3 versions
1) Oopswares port of picodrive
2) my port of picodrive
3) my port of genesisplus
I also have no idea which version is which but that should be obivous. IIRC, the code in the megadrive directory has the most compatiblity graphics wise but the sound was really f***ed. Also I am 99% certain that this code is also out of date with a newer version on my laptop which is currently on the other side of the country.
Anyway, take a look and let me know if any of the games run better.
EDIT: hmmm, file attachment limit. I don't have my ftp login details to hand either so this will hopefully do.