The first big test would of course be Holyfield. Tyson of that fight would be near his damn best, be interesting to see Evander against that version.
If he had emerged at age 20—starting with the McNeeley fight—he would theoretically have dominated until around 2003 and remained a significant figure in the boxing world for several years after that. I say "theoretically" because, in reality, he would have run into trouble much sooner. If he were 29, then—aside from other issues—he would have experienced the decline in form typical of a fighter with that style; a 30-year-old Tyson would never have been as good as a 20-year-old one, even without the prison stint.
I never bought the fairly common conceit that Holyfield would always have Tyson's number. Best I could say is the enhanced/Evan Fields version had a decent chance against Tyson. But I think Tyson had declined quite a lot by the time they fought. With the extra movement & endurance + better punch selection I must favor Tyson. Especially if rules against excessive clinching are enforced. Without PEDs Evander would have little chance. He needed to be able to hold his own & ideally manhandle Tyson.