I already said this previously, but I heavily disagree with the idea of creating a new key for her.
First of all, her being stronger than she was in Endgame is just an assumption. There is no mention of her being stronger, no statement of her training, no training montage like with Thor L&T, no power up between the movies, no power up in the movie, nothing. So, saying that she suddenly got millions of times stronger is just pure speculation.
Second, even assuming she did train, that would hardly explain a boost in power of millions of times. She had five years between the beginning of Endgame and the end of Endgame to become stronger, in a period in which she had much more reasons to become stronger, yet she couldn't grow in power enough to one-shot Thanos. And now suddenly she becomes millions of times stronger than Thanos in a single year (or maybe two, I don't remember when the Marvles takes place, but the logic is the same). It would be non-sense to assume such a thing.
There are two option, in my opinion:
- The calc is correct and valid, everyone that is currently High 6-A becomes Low 4-C.
-The calc is an outlier, and the High 6-A calc of the energy of the Sun per second is used instead, leaving everything unchanged.
I am neutral on which option is the better one, but for sure I heavily oppose the idea of a new key for Captain Marvel. That would be reliant on pure speculation and headcanon, until further notice.