Luffy new attack. Not new form. After Sulong King being only furrier don't expect nothing special about it. Would just be some shit as Rec Roc with Adv CoC. He didn't named any of his Adv CoC attacks.
Luffy new attack wasn't strong enough to beat Kaido, then Kaido knock him out. Not sure if Kaido knocked him out and pushed him off Onigashima or Kaido's hit sent him away so hard that he felt from Onigashima. Both would be coherent with Kaido statement at 1013. So probably both are wrong since Oda doesn't work with logic.