Ghidorah species is the strongest in the monsterverse. King Ghidorah from 2019 was the youngest, weakest and smallest of them all, just imagine older, bigger ghidorahs and their powers. Ghidorah(species) is the most powerful in all of monsterverse.
Yeah, Modine posted Heisei images of the Shobijin and SpaceGodzilla. The former was already teased in a similar manner, when Dever posted emojis of two fairies and a shooting star.
Yeah - he's owned by multiple parties (depending on the part of the Kong franchise you're talking about), but the only one relevant here is Warner Bros.
Toho doesn't own Kong, so they have little say over what his owners want to do with him.
Besides, it's been stated in other Kong media - such as the 2005 film by Peter Jackson (unrelated to the Monsterverse) - that there were other Kongs in the past and "King Kong" is the last of his kind.