Eventually his power always seems to come through, but his power hasn't been special enough to get some of the better fighters he's faced down until the later rounds, it seems to take him time to find the right shot. He was landing big shots on Spzilka, Duahpus and Stiverne and for the most part they were soaking it up. Spz looked like he could take the power until he got cleaned with a ridiculous shot.
I think his undoing against the best guys will be that he's not going to have time to get his power off, he can definitely KO a guy early if he lands the right shot, but it's less likely than him getting caught and overwhelmed imo.
Joshua seems to have the more George Foreman style power in that he hits like a truck with both hands and when he puts them together, most guys fold. Wilder is more like a HW Tommy Hearns. Wlad still hits like a truck too, especially when he generates a lot of snap on the right hand. I'd still put his one shot power in the same category as Wilder and Joshua.