The SCLogin module doesn't duplicate the K2 Login module's functionality. We do have a User Menu option in the SCLogin module where you can select a Joomla menu to display to a user after they've logged in. That allows for a lot of flexibility as you can add any menu items you want, not just those that are specific to K2.
If, however, you don't want to use the User Menu option in SCLogin, I'd recommend you configure Joomla to only show the SCLogin module to non-logged in users. Then, configure the K2 login module to be shown to Registered users. That will give you the options it sounds like you're looking for.
I hope that helps, but if not, let us know.
Thanks,
Alex
JBC SC Login and K2
