It's not that I'm trying to pick and choose, but I don't know of any other piece of Disney canon evidence that tells us the level of power Anakin was on by rots (aside from the novel itself, which I know there is a lot of gray areas with the novels).
Disney makes Vader's power very clear, but Anakin? Since I don't know of anything, I just refer back to it until something better comes out... Unless there actually is something that I don't know about. The "light-years" quote is new to me.
^
Well, the one closest thing that I can think about is Yoda's vision from TCW. Anakin was strong enought to beat Dooku and yet he wasn't much a factor against Sidious. Anyway, that was just a vision, so I'm not sure if we should treat it that serious.
Vader has a vision in a Disney comic where he defeats Obi Wan during their duel on mustafar, implying that he’s>Anakin. But like you said, visions aren’t completely reliable