In Revolution, Roles are only important if you want to give different capabilities to different users in the same user group. If that's not the case, 'member' should be fine, though I would probably create a Role with an authority level of, say, 10 and give them all that Role in case I wanted it for future use.
In Evolution, OTOH, Roles are critical in determining the users' possible actions.
It sounds like the only reason you have user groups at all is to make it easier to find the users. Will these users be logging in anywhere? If so, and you're using Revo, that will determine what kind of ACL entries (if any) you need for them.
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