Well,
generally armor gets absorbed into druids new form. And druids cant wear metal armor.
But if you do have "dragonhide" plate and its magical and you're proficient with it, it would be logical to have an AC of 18 +whatever magic bonus armor provides and the feat would work then IMO.
toughness is affecting druids own HP, so this would be double effect, so no. You could house rule that the feat affects only HP of wild shape forms but that is up to your group.
all other feats should work if your body is able to perform them.
I.E. polearm mastery would work if you shift into an ape, not so much for a goat or a spider.