Fury can definitely get knocked down, we've already seen it a few times. But he'd always just spring back up and win a fight. He also had some controversial wins, like the first one against Wilder that you mentioned or his last one against Ngannou. But he has a perfect personality for this profession. He truly believes that he's meant to be the undisputed champion, which gives him extra powers.
As for Usyk, his technique is second to none, but the size disadvantage will be the major factor here. You don't need to be an expert to know that Fury's main tactic will be throwing a LOT of jabs to keep Usyk at a safe distance.
Usyk should be prepared well when it comes to this fight because Fury is never was a fighter he fought in the past, he should prepare for a mental fight with his preparedness of some skills to get out from that simultaneous hugs from Fury that could potentially make him tired easily because if he don't he will be tired and eventually fall to his ground due to being exhausted and can't seem find a way to beat Fury.