Freddie Roach (I think) said that only suckers get hit with he right hand (as in, without being set-up through the jab.) Similar thing was said during a Maywather fight. You can't find him with a jab, you ain't finding him with nothing. Couldn't be more true regarding Joyce. He needs the left hand active and effective.
Joyce would batter Whyte, especially the current version of Whyte. Whyte has a punchers chance with his counter left hook but Whyte is smaller than Zhang and isn't a southpaw he couldn't take away Joyce's jab like Zhang did. He'd get out jabbed, walked down and stopped.
It depends how badly these 2 fights have ruined Joyce mentally and physically. But assuming he's anything like he was in the Parker fight he destroys Whyte.