He is very strong indeed, but I personally think he is more of a volume puncher, overwhelming his opponent with tons of punches and being relentless. He definitely has killer instinct, if he hearts you, he will finish you. I would say p4p, currently Inoue or Beterbiev.
Probably Wilder. Not sure they keep such a Stat, but he'd be the guy with the most one-punch KOs off the top of my head...
Overreaction sunday on ESB the guy stopped a 40 year old and you think hes the best puncher in featherweight history lmao. He has 17 KO's in 24 fights against bums (other than Warrington) thats not an impressive ratio specially considering the quality of his opposition. As for the question Its Wilder followed by Inoue.