Restrict the usernames, email addresses, characters and symbols or email from specific domain names or language in registration ...

Allows administrators or capable users to change the users profile url.

This plugin will enhance the security of your WordPress.

Allows an admin (or capable user) to edit the author slug of a user, and change the author base.

To prevent that usernames are publically visible, the username in the author's permalink is replaced with the author's ID.