It's funny how Phineas is seen as like, the more socially adjusted one and Ferb as the socially inept one (especially in regards to autistic Ferb headcanons) but imo I'd argue they're the opposite.
Phineas is more outgoing and kinder and friendlier, and has more friends, but he's also the same kid who can't understand basic social cues everyone else can (Isabella wanting him badly, Candace wanting him in trouble, etc.), and he likes doing the same thing everyday, just building and having fun. Aside from Perry, he's the only character to not really express or desire any form of romantic love (save for some sparse moments with Isabella in specials).
Ferb on the other hand seems to be moreso quiet by choice, he's extremely well spoken and knows more than he lets on socially. he displays a level of snark far above his age, and acts older than Candace.
(obviously autistic headcanons are fine, i support them and i see ferb as autistic too, just find it funny when people see phineas as somehow socially better in comparison)