I mean it depends. Cruiserweights nowadays would be large enough to compete with the significantly smaller heavyweights of the 70s. Norton weighed more than any of Usyks Cruiserweight opponents but not by much. Regardless I'd still favor Norton would win a decision
Well, this is cos prime Usyk's version had best his marquee wins via decision. Okey, Bellew and Huck he had stopped, still best opponents he had were then in prime Briedis ( barely had won this one, razor close if to be fair ) and then injury free prime Gassiev. decision wins. Other boxers: Vs Hunter who then was undefeated, he too had decision win, then also UD win vs prime Glowacki version in Poland ( 29-31 y.o Glowacki was prime Glowacki version, not later ). Despite he had fairly enough power for CW division, in one period he had 90% stoppages at CW ( before Hunter fight I think ), he had agility and speed advantage in this division and looks that used this. If boxer wasn't top5 or wasn't in best shape, he stopped CW boxer, if it was good material for division real top, then decision wins.