I don't trust those little plastic slugs for drywall!

They're tricky to install and eventually they wind up chewing up the hole they are stuck in to the point of falling out - no friction!! I've had that happen many times (thank god I don't live in one of those cardboard boxes anymore (gypsum board is another issue entirely, I've always preferred metal mesh & cement and plaster interior walls). [Linked Image]

They also have no gripping power, so if you use these to mount an outlet box, you'll be sure to see that box dangling from the pipe after repeated plugging and unplugging appliances from that socket.

Maybe those metal inserts - with the wings that bend back against the side of the plasterboard facing the studs would work better (I believe they're called toggle bolts) as you tighten the screw?

Although who knows how good they are for holding up conduit and boxes...definitely a step up above those plastic inserts you mention.

Just my humble opinion.