I haven’t gotten there yet, but does the Hall of Fame list your Pokemon’s movesets like they do in every game post Generation III? I remember being disappointed in Pokemon Fire Red and Pokemon Emerald when I beat the Pokemon League, only to discover that the Pokemon’s movesets aren’t recorded.
I ask this because Mega-Eevee has four move slot syndrome so I want to plan its movesets in a way that gives each Eeveelution time to shine (which of course means I plan to battle the Elite 4 multiple times with it) but I don’t want to discover that said movesets don’t show up after beating the Pokemon League.