The TTL question may be based more in personal experience than scientific data. I have heard that Godox TTL underexposes, I've heard that it overexposes, and I've heard that it's not as consistent as Canon's speedlights.
For me and the way I shoot TTL (weddings and events) I find the AD200 to be just as accurate as the ex600rt. But, I also find the ex600rt to be inconsistent. So I am saying that the two are equally inconsistent in my experience.
I know wedding photographers who shoot TTL and don't feel the need to adjust exposure in post. I do. With both systems, I always feel the need to push or pull exposure (at least a little bit) with either system.
Maybe that helps, maybe not...