A drip edge is not a gutter.
I have zero condensation issues with the metal roof on my coop and I live in a quite humid climate. Heat gain? Hot outside is hot inside here so I don't worry about it. If the coop roof was painted instead of silvery galvanized I might.
FWIW, my coop has a galvalume roof over joists and purlins. No insulation or sound deadening. My chickens haven't complained about noise when it rains. Sometimes I'll go down to my shed that has a galvalume roof just to listen to the rain. Quite soothing, but then again I grew up in a house...