I feel like most of the time I can't differentiate between the "social anxiety trope" and just simply being "extremely shy trope"
(the symptoms usually come and go)
I'm not sure about the "best", I'll just put one that I read recently
silent witch
there are many that I thought to be in the "social anxiety trope", but when I skimmed them back, I'm not so sure anymore
for example, I thought Noraneko to Ookami was one, but then I guess it is not
edit: I might've mistaken Noraneko to Ookami for Haru no Arashi to Monster, both from the same author, but still
there's also that isekai girl who lives inside a magic box because she can't speak face to face