Best boxing? No. Heavy hands? Yes. But he never really set anything up. He just walked Miller down. He's lucky Miller didn't throw more leg kicks because the two he landed knocked Mein off balance.
Both times he hurt Miller, the shots were set up with jabs. I would say he's more quick and accurate than heavy handed. Cyborg murdered his legs but his boxing overcame in that one. Very similar to the Diaz fight, actually.