stay at 4.1, no benefit at all on higher versions.
you can use the updated softmod any wii guide by mauifrog, link below, to set up your wii again.
if you are fine with the drive leave it like that, however i switched to fat32 loading to have the apps on the hddas well, instead of having them on the sd card.
music games in general need some more attention, find the IOS to use/load the game setting in your loader and try 223 for example (if that is set up properly) and/or read here: Music Games
gx 2.0 caused some trouble for some users, you might think about switching to config usbloader for example.
there is no general do that do this and everything is working routine, mod properly, have a good loader and the rest should be "just" altering some settings like IOS, and videomode, good luck for no.