Just a thought...
In the anime, Goku has been clearly more powerful than Vegeta since the U6 tournament arc, since he has Kaioken Blue up his sleeve. On the other hand, in the manga, Toyotaro has been clear not to put them on separate tiers:
• During the U6 tournament, no Kaioken, and Whis comments that Vegeta was fighting at 1/10 strength vs Hit
• Goku used the SSG->SSB tactic during the tournament, and Vegeta matched it vs Goku Black
• Goku achieved mastered SSB against Zamasu, and Vegeta used it when training with Beerus after the tournament
Now, during the anime, it's possible (and perhaps likely) that Goku's UI and Vegeta's new form are not equal. It's actually interesting, the ending has conflated Vegeta's form with Goku's UI, even though it looks on par with Goku's Kaioken Blue (standard, or x10 or x20, whichever he's using against Jiren right now; presumably x20). The Grand Priest and Whis also called it his limit-breaker form, the same terminology they used to describe UI Goku. It does seem a lot like Trunks's rage transformation in the anime however, while UI appears to be something that will appear in the manga as well. Regardless, at the most, Goku and Vegeta are close in the anime, and at the least, even if they aren't, it's being suggested it's not a massive gap in terms of dialogue/perception.
This is all setting up the manga to finish with Goku and Vegeta being a tier apart at the end of super in the manga, even though they were close all-along. UI Goku will very likely still happen, but Vegeta's transformation might not.
What am I getting at here? Not all that much, but I do think it's interesting, that after seemingly artificially reducing the gap between Goku and Vegeta during the course of the Super Manga, Toyotaro will likely end up with a larger gap between the two than there will be in the anime.
(Of course, if the transformation isn't anime-only, or whatever happens in episode 126 as suggested by the title, occurs in both the anime and the manga, then all this is moot.)
What is canon? Everything written by Toriyama: Jaco, Dragon Ball Minus, Dragon Ball (42 volumes), Dragon Ball Super (his outlines). His statements from guidebooks and interviews are canon as well. Newer material retcons/replaces old material.
What is not canon? Everything else. Particularly GT. Doesn't mean the material can't be fun or entertaining (a lot of it is!), just means it's not part of Toriyama's vision.