I understand why you would think that, but it isn't actually correct.
Gold compounding heals spiritually, cognitively, and spiritually. For example, brandon has confirmed it could heal a shardblade, or even a hemalurgic spike wound.
Physical is just what's visible.
(It's been a little while, so take this one with a grain of salt please)
Gold compounding wins
Gold compounding has no effect, so I guess crucio?
Copper wins if draining enough, imperio wins
Hmm. It depends on strength, I suppose. Generally, I feel like dementors are stronger, but a decent misting who's flaring could probably beat it?