Hmm, I think I am not following. Why using msys2 bash on top of WSL2?
You either using WSL or cygwin/msys2.
GIT is slower on cygwin, especially stat() with do hacks to check for +x mode. But once cache is warm, it works fine. Albeit, I didnt used GIT under Win10 from quite some time, im doing most of my stuff on older windows using my very old Cygwin fork thats is more snappier :)