I personally don't
believe anything, but I do have some thoughts on certain things.
Vergeben has been scaringly accurate with his leaks. While I don't take his or any leaker's words as gospel, his claims tend to be the ones I consider the most thanks to the previous reveals he's done. With that said, the fact that he failed to guess most Echoes (he only got Lucina and Dark Pit right so far due to his claim of every Smash 4 character coming back) makes me think that he only has part of the game's information, so even if he's right, he clearly doesn't know
everything, so there could be more than what he's saying.
Music Theory offers an interesting pattern, but to me, I feel like it's such a Sakurai thing to do to just break patterns, like what happens with the pattern of someone dying in each trailer. However, I
do think it's odd we never got a Pokemon remix in the website despite the fact that we clearly heard a Gen 7 Remix of the Trainer Battle theme in the August Direct. So far, I'd say all Music Theory confirms is the very much expected Gen 7 newcomer.
loz18 is someone I'm cautious of. He got a lot of stuff right in the Direct, but after that? Nothing. Not saying he's a phony, just that he's been really quiet, compared to Vergeben, who's always been confident of the stuff he's claiming to the point where he says stuff like "any leaks without [character] is fake"
I don't believe the Box Theory at all aside from its implication that we're gonna get an Echo of a Smash 4 newcomer, most likely Ken as an Echo of Ryu. Artwork is not final, especially with the lack of Isabelle, so it shouldn't be taken as gospel.