If they fight, Fury will overpower Usyk just as he did with Wilder by being on the front foot and getting Wilder to walk back. I think you are spot on when you say speed will not help Usyk because when Fury hits him he will feel the impact. Not many would give Usyk any chance of beating Usyk but before that fight can take place he needs to defeat Joshua in the re-match and also Fury must defeat Wilder in their re-match.
I still see Fury being the one who walks away from the as the unified undisputed heavyweight champion before the end of 2022. Maybe a fight or two in 2023 before he retires.
I feel like even at this age, Fury has got one of the better powerful hands, to be honest. Yes, Usyk is very agile, but how long will that help him, once he gets those hands on him, he will be trying to back off and only then Fury will overpower him and try to finish the game. But before that, in the rematch, I'm hoping that Usyk will win over Joshua as he seems like he can counter Joshua pretty well from what I have seen. And Fury also should be winning vs Wilder in the rematch.