To gain root access to a server all you need is the user id and password. Since the default root user id is 'root' that leaves only the password.
Not so, you also need access to the system, either physical access, or network access to something which accepts the root password. By default, that is nothing!
How do I change the root user id to something less obvious and create an id w/o privileges named 'root?'
Same goes for admin id.
You will likely break a lot of things if you change the root user id.
Choose a very good password, and keep it to yourself.