1: No. Being a bowser main isn't required to understand bowser. I have a strong bowser second. Even if I didn't, I could just as well play against the character or as the character + watch videos to get a good understanding of him. You don't need to main a character to know when they have been buffed, or when they need buffs. If the only people with viable opinions on their characters were those character's mains, almost no character would ever get nerfed.
2: I think bowser was more buffed than nerfed. Slightly.
3: I think his MU spread is more normalized, closer to even on most really bad matchups and really good matchups from before while his close to even matchups are barely changed. Speed is a universal tool in smash, it can be used to deal with almost anything, and bowser gained a great deal of speed in 3.6. Therefore, there are going to be matchups he previously did not have the means to deal with that he does now. What he lost were tools that polarized his matchups, like excessive armor/reach.
4: It doesn't matter whether or not any big bowser names changed their mains. Main swaps come with every big change to certain characters, regardless of whether or not they were actually nerfed, because you see aspects of the character lost that the players in question may have enjoyed, or you see aspects lost that were abusable and mediocre players no longer succeed without them. Not to suggest that this is the case with bowser, not in totality anyway.
disclaimer: I still don't think bowser is an amazing character currently. I just think he's better off than he was before. I'm just a little sick of hearing the bitching from like 90% mediocre players (particularly you) and barely any actual feedback from the good 10%. It's not okay to say "This character was mostly nerfed, and here's how I know why, I lost to a guy a normally beat!" and expect that to be valid reasoning.
