It's safe to remove channels you don't want. You can delete them through your system menu like you would any other channel or you can use Wad Manager to uninstall them.
I hacked my wii and installed homebrew, usb loader gx, and neo something. I have recently installed a new loader. Can I/ should I remove the old channels. If I can remove them, how do I do it?
It's much better to uninstall them with a wad manager, since deleting them through Data Management can cause a semi-brick. I explained it here.
"Macs are the Perfect Computers," said the Perfect Idiot.