Don't be naiive. Fury does not like southpaw's and he's never been in with one that moves like Usyk.
The ideal scenario for Fury is an all UK fight against AJ and I'm not entirely sure he fancies that really but he knows damn well he has to fight the winner whichever way it goes or he'll get called out for bottling it if he doesn't. AJ is the easier of the two.
Fury doesn't have big power, he'll struggle more with AJ than he did Wilder for sure. If you take Wilder's big over-hand right away, he can't box, he has nothing else. Fury knows AJ has some power and will be able to take Fury's not so hard shots.
Usyk is another problem altogether. A very tricky southpaw with incredible movement, a great chin, and power to boot.