Not really, particularly if you don’t want to hide discussions by using groups to limit user posting rights.
A group is a shorthand form for identifying a list of users. You can use them as security, but that becomes cumbersome pretty quickly.
Just get your users to join, they will post in categories which interest them, and ignore those which don’t. You don’t really need to limit them with groups and permissions… people just naturally show interest in what they find interesting.