Keep in mind that "creating a user" in that console (and in Firebase Simple Loign email / password auth. in general) only generates a new mapping between an email address and a password, and gives that account a unique, auto-incrementing id.
Firebase Simple Login will not automatically store any data in your Firebase, though upon login, it will automatically generate a new Firebase auth. token against which you may write security rules making use of the auth
variable.
Login methods using any other provider currently store no data, though in the future there may be more functionality there. Logging in with Facebook / Google / etc. will also fetch a bunch of useful user metadata and send it down to the client, in addition to creating a Firebase auth. token for use in security rules. To see the contents of the auth
variable across all providers, see the 'After Authenticating' section on each of the Simple Login Providers docs pages, for example: Facebook. There is no notion of a delete for any provider except for the email / password provider.
If you'd like to have user accounts that are linked to multiple social credentials, it can be done, though it is a little clunky (and manual) at present. See How can I login with multiple social services with Firebase? for a thorough walkthrough.