All depends on which skill, there's more than one. Ortiz - Counter punching, punch selection/accuracy, timing, distance control. Povetkin - Attacking footwork, punch selection/accuracy. Takam - Upper body movement, head movement, punch selection/accuracy. Hughie - Defensive footwork, counter punching (the timing of his uppercuts against Parker was excellent, he just didn't throw anywhere near enough of them). Ruiz - Timing, punch selection/accuracy. As for the champions I think Joshua and Parker have pretty good combinations, backed up by their power and hand speed respectively but other than that there's not much to write home about on a technical standpoint. You probably don't need to ask what I think of Wilder's technical ability.
1) Bodybuiltony Joshuaua & Alexander PovetKing 2) Jarrell Killer 3) Adam Cowboyski 4) Carlos TakambeatParker 5) Daemontay Marijuailder