some games doesn't work at all (Castlevania for example) on EmuNAND with USBLoaderGX (it requires Sneek environement).
Install them on Real NAND and use the loader to list both Real and Emulated NAND.
If you want to install some games which require old/different cIOS on your EmuNAND, it's a bit more complicated.
The (Quick, not a details tutorial) steps are :
1 - the cIOS
install all needed cIOS (rev17, rev19 (base 38 I think), d2x (different version have different compatiblity) in different slots on your Wii. preferably in the 240-250 range.
2 - The Emulated NANDs
You have two choice:
2.1 - put your EmuNAND path on the root (all the folders on the root, not inside /nand/ folder)
or
2.2 - use two different EmuNAND path : one on the Root (to use with cIOS rev17/19), one in a subfolder (/nand/ to use with cIOS d2x)
Note: old cIOS require the NAND to be on the root of the first FAT32 partition of the 512Byte/sector drive. subfolder support was added in rev21, multi-partition in d2x v3, 4K sector in d2x v4.
3- The Titles
Install problematic games in the EmuNAND located on the Root
Optional : If you use the dual path (root + subfolder), then install the problematic game in both EmuNANDs.
4- The Settings
Go into the problematic game's Settings to set the cIOS to the slot where you installed the required cIOS version (if you installed rev19 in slot 240, set the N64 games to cIOS 240)
Optional : If you use the dual path choice (root + subfolder), then also set the problematic game's settings "Nand path" to the root.
Result :
The USBLoaderGX will list all channels found on the "default" emuNAND (/nand/), using the default cIOS (d2x):
it will also see the problematic games as they are installed on the default EmuNAND, but these problematic games have a different setting : IOS and path