superuser_reserved_connections and max_connections

We were getting a lot of "max connections reached" errors and noticed that all our users are super users, after some digging I found the 

superuser_reserved_connections parameter was not set (default to 3) this lead to some additional questions:

If all my users are  superusers are they effectively limited to the number of connections defined in the 

superuser_reserved_connections  parameter?

Is there any significant difference between a superuser and non-superuser connection?

Any additional insight would be great.