Why Sanji fights King means Sanji had CoC?
Because the Beast Pirates are ranked by Meritocracy. Jack is stronger than the Tobi Roppo and thats why he is a tier above them.
King and Queen bully Jack therefore they are above him. King looks down on Queen and Queen doesn't deny.
King is Kaido's right hand man. Queen is Kaido's fuck up.
Marco is fighting King whereas Queen was fighting Chopper.
Kaidos crew
has to have Conqueror's given that he himself stated,
"We don't need that many conquerors"
Given the set precedence that Big Mom has a right hand that has CoC and that Benn Beckman is
equally feared as Shanks (presupposes he has CoC as well) fuels the theory that King (a strong swordsman) in the land of Swordsman with the name
King would have to have CoC.
Also some Ryuma stuff but that applies to Zoro.
Anyways if Sanji fights King with or without help and is
the one to finish off King, it pretty much means he will also have CoC awakened this arc.