I'll give you my experienced opinion (if I do say so myself).
Anthony Joshua vs Usyk
Both boxers, AJ is more of a boxer puncher, AJ has height, reach and weight advantage, hits harder.
Usyk more skilled but his extra weight will slow down his speed, his boxing will be negated by AJ's reach and the risk he has to come up top with AJ's height.
Result: 12 RD decision for AJ or later round stoppage 8-9th onwards ......... but my money's on a points win for AJ.
I don't see any way for Usyk to win because to win he'll need to pull off combinations to rack up points and I don't see how he can close enough to AJ other than pecking one and away single shots.
If Usyk does overcome all of those disadvantages and wins ............. then he's quite possibly the greatest of all time, def in the conversation at the minimum.