He's a creature(probably a wolf) who ate the totem totem df. He is his crew's source of power-up. Kinda like grayback from battle realms,only that grayback is a human from the wolf clan. Or kinda like a serpent/dragon who ate a pheasant pheasant df(Kenji). Or a witch like Yvaine or Zymeth from the lotus clan. But judging from the island where we saw x drake and caribou, I think kaidou is a robot, or something created by technology. I think he is a robot with a human brain,a cyborg like franky or kuma. Or he could be a robot created by vegapunk who then had its own way of thinking but same knowledge as vegapunk.
I don't think it's Typhon. That's a Titan, thus a god, and a whole new level of mythical Zoan. But my guess is close to Typhon, however. An offspring of his in Greek mythology.
Mythical Zoan type: Chimera
Chimera are mythical creatures that are a combination of a goat, serpent and lion. But nowadays the name is used for most amalgamations of animals. Kaido of the 100 beasts? His Chimera fruit allows him to morph parts of his body into whatever animal parts he likes. A worthy fruit of a Yonko, and probably the most powerful Zoan fruit.
*Waiting for BB to come in when Kaido is defeated to steal his fruit.* :P
100 beasts = king of beasts = lion possible. Sign of the beast (serpent /dragon) maybe. I am gonna throw out a completely different idea and say that he is a giant centipede that at a human paramecia. Mainly because that would be awesome and the transformation forms with 100 legs would leave a lot of very dangerous configurations.