fbneo_cps1.dol = Updated CPS-1 emulation, supports 3P Final Fight romhack. The original is kept in case speed/compatibility changes too much.I see many other arcade cores in Ra hexaexo: I don't know what purpose they are serving. The lack of any kind of documentation doesn't help.
fbneo_sega.dol = FBNeo doesn't fit on Wii, this build only includes some SEGA drivers (System 32 was the goal but it doesn't work.)
fbneo_20pacgal.dol = Similar to the reasons above, this combo version of ms.pacman/galaga doesn't work in the other arcade cores. They have this machine in my local arcade so I thought it would be cool to have it on Wii too. They're the same exact games with very minor differences.
mame2003_midway.dol = https://github.com/libretro/mame2003_midway but I can't tell you if it's any useful.
mame078.dol = It's shrunk MAME 2003, only there for compatibility.
sailormn_fba2012.dol = If you use FBA to load this game from the System Menu, the game starts without the wiimote connecting. This build removes the huge game list and many unused drivers, and brings the file size from 12.5 MB to 1.6 MB, it loads faster and the wiimote gets recognized.
segasonicbros_coreD.dol, pacman.dol, tmnt_xmen_twin_ultra_coreE.dol = same as above.