Sorry for double quoting/posting, I followed the guide to properly format another SD card I have (4GB) and tried 3 different Roms for Sonic Advance 2 (US/JAP/EU) with TempGBA and they all gave me the same results, running really slow in the third level (music level) and game crashes completely if you bring up the pause menu.
I tried another GBA emulator I heard about, NDSGBA, but I can't get into the title screen because it uses a buggy version for MGBA that doesn't read the start of both Sonic Advance 1&2 properly but instead gives you this broken multiplayer screen on start up, this could be fixed if I could enable the use of Bios but it doesn't seem the emulator supports it, Sonic Advance 2 is unplayable with TempGBA, all 3 regions, who marked it green in the compatibility list?