Both vCOPS Standard and Advanced editions have vSphere UI only, however the Ent and Ent Plus editions have both vSphere UI and Custom UI. The access to vSphere UI is based on the access rights defined in vCenter Server. On the other hand vCOPS Enterprise and Enterprise Plus editions have a separate Account Management function. You can create local users or import users from AD and provide them access to the custom UI. You can also create role groups in custom UI.
Ok I guess what I'm looking for then is what rights in vCenter give access to vCOPs? I seem to recall some screenshots of a role that's created when you install vCOPs but I don't have that and I don't see any specific vCOPs permissions to create a new role like there are for say SRM. The documentation I've found only relates to enterprise.