Deepa the Registered group is designed to be almost featureless. It is just a switch from Unregistered to member. It can have much the same capacity in real terms as an Unregistered guest. So as a Reg. you may only see certain areas, and be unable to post, PC etc.
It's the secondary groups that give functional abilities.
Note of warning dont use the red NO on permissions at usergroup level. Anyone who has a red NO will override other usergroups they belong to on that permission ie block it.
Use the grey INHERIT permission instead.
The way I understand it I have a fundamental fork at first level between unregistered and registered.
Unreg have some red NO but when they switch to Reg. that disappears. All their secondary groups are grey or green permissions.
I have a small number of key secondary groups. These divide us into admins, moderators, and 3 other types. All members will be in one of these second level memberships. These determine the main access areas, and of course admin and mod abilities. Also level of PCs, signatures etc.
Then third level groups add additional privileges like editing articles which dont fit the main group structure.
There are also permissions attached to nodes where you can set access or abilities for that node. You do that from the node tree, look right for blue box Permissions. These permissions will not affect the groups you edit there, except for this one node.