Original/unaltered VC WADs should be pretty safe (about the same as HBC, yes)
On the other hand, injected (or otherwise altered) WAD's you'd have to be careful with since if they corrupted the banner when they altered it, it could cause you a vWii mode brick.
Basically, if there's a safe place you can test them in first (like a USB Loader w/emuNAND or Dolphin ... or on an original Wii with xNEEK or some brick protection like PriiLoader/BootMii@Boot2), that would be ideal.