>Galar has bigger leaks so Farfetch'd in there are stronger
>Meteorite impact killed all Corsola
>Darumaka lived in the cold for so long it can no longer produce fire
>Yamask has Norse-esque runes instead of Egyptian-esque masques

To me these seem like the only regional variants in Galar that make sense, all others don't seem to have really a rhyme or reason to change, or if they do, it's a very far-fetched one (like Meowth's). In Alola all regional variants had plausible reasons to change, they dropped the ball.