Joshua did what he had to do to win, but that shit ain't going to fly when he fights Wilder.
The strategy wasn't for Wilder though, was it? It was a strategy to beat Ruiz. He made sure he never got caught in a brawl with Ruiz because he knew he might come off second best. He kept his distance using his jab and used his height advantage to good effect. He kept moving not giving Ruiz a chance to set himself. Also, the fact that Ruiz gained weight played right into Joshua's hands. Joshua lost weight to make himself more agile and faster. And because Ruiz gained weight it just made him slower on his feet.
I'm not even sure there is a perfect strategy to beat Wilder anyway. All Wilder needs is one opportunity. It doesn't matter what the strategy is, if at any point within the fight Wilder gets through, it's game over. I mean, Ortiz out boxed Wilder in the last fight for pretty much 6 rounds. All it took was one punch from Wilder and that was it. Maybe Ortiz got a little too confident, but... to not allow Wilder one opportunity to land a big right hand is asking a lot. Not that it can't be done mind you.
One thing that isn't mentioned is Wilder's jaw. He has been shaken by a few boxers including Ortiz and Fury, but as of yet, he hasn't gone down. And that is something to note because maybe the way you beat Wilder is to knock him out before he has the chance to.