Wladimir and Vitali would both be 5-10 years younger and not retired. Both fighters with great potential, who unfortunately suffered from severe injuries Denis Boytsov and Magomed Abdusalamov are still in the game. Mike Perez would have stayed the same, since the Mago fight he was clearly affected and never got back. Tyson Fury still up there, in great shape, motivated. Andre Ward moving up to HW after getting wins in CW. /////////////////////// I don't think much would have changed. Fury would be #1 one, AJ would be targeting him. Both may be the #1 and had to fight each other for the spot. The Klitschkos would follow. Wilder wouldn't have been a Top 10 fighter.
So basically you are asking how prime Ks would do in this era? Nothing else seems to be a meaningful change. I'd pick Vit to come out on top.
Alternate version of Guido Vianello doesn't lose to a Cuban at Rio Olympics. Proceeds to beat Hrgovic and Yoka and wins gold medal. Fast-tracks through 2017 and wins world title in 2018.
Vitali and Vlad would be the champions, no doubt about it. SOB had to cheat to get wins over Kovalev, very low blows, they are illegal. SOB will not fight Joshua, he would be crushed! Usyk would kill him and Kovalev would love a rematch in neutral territory with neutral judges and referee, but SOB said that neutral judges would be unfair.