If I created a Udemy account with my Gmail, then what’s the difference between signing in with email and signing in with Google? Thanks in advance.
Adding on to this comment, it is very often not possible to change your auth method.
If you use email to register, you can almost always change to a different email (same method) but you can’t change between methods, like from Google auth to Apple auth, or even to a different google auth.
You’d need to create a new account, and therefore lose all the data on your old account.
Always choosing email gives you the most control and most privacy, I’d strongly recommend it.