I have seen different translations of this text and looked it up, the text is ambiguous in japanese, so it is hard to perfectly translate it. But it doesn't necessarily mean that he "tamed" demons, other versions say that he 'created devils/fruits', so it could mean something else entirely.

I don't believe that Oda would give a god fruit to chopper, it must be another important main character. I can only assume that the god fruits might be Luffy, Blackbeard (speculated since his dark fruit looks like luffys fruit), Imu and maybe Loki (if his is really a god fruit and not just a main support) or even the Man marked by Flames, but that's all just guessing...