I'm trying to clear up space from my wii. Is it safe to move the wad channels I installed with WAD Manager to an SD card and back like any other wii channel?
Depends what they are.
Wiiware/VC - Yes and is built in support for this in 4.0/4.1
Channels eg USB Loader, Neogamma - Just delete the channel using Wad manager and use the boot.dol on SD to laod the app.
IOS - Never remove any, ever or you'll likely brick.
Saves - Yes
Not really doing much Wii stuff these days.