Yes bash scripts still work, but I heard there may be other things that randomly break.
Many things use for example, which often is a link to bash, but may not work anymore.
chsh does not modify /bin/sh
Maybe you’re thinking of a certain video from a certain YouTuber who linked /bin/sh to fish?
Haha no didnt think of that? Hm, I dont know why it would be an issue then. POSIX compliant shells should be no problem, but I wouldnt do it for fish