EZpublish has a pretty good access right system. By default an user cannot do much unless you especially give him more permissions or move him into an group that has more permissions.
You can find information about that here: http://ez.no/doc/ez_publish/technical_manual/3_8/concepts_and_basics/access_control
Although I think it is more informative to just have a look at the roles that are setup during installation.There you have already an admin with the respective permission set and a set for anonymous users. I think there is also a ready role for editors (this might depend on the package that is installed).
Each user is an object so you can edit the class if you need to store more information. One big minus for EZ is that it is quite complicated to have different user classes. So if you want to automatically give some users admin rights and some not,this will be difficult. Generally though there is only one registration form for all users and the admin has to give an user admin rights manually if required.
