Questions:

Is there a page around here somewhere that lists the current set of membership benefits, with details about how to access them and/or verify that I have them installed/activated?
For example, how can I know exactly what extra members-only modules are available at any given time? Exactly how do I access them and/or verify that I have them installed? When I log in to the site as a member, the members-only features are presumably available, but it isn't obvious to me what those are. Neither is it clear to me what runtime features of TR are membership benefits, or even if I have them activated.

Answers:

The following page contains the list of modules delivered, free or licenced users / members only.

TR will check at the interval specified by you to see if new modules are available or not. At any time, you can go under Plugins, Updates and Available Plugins Tabs and press the Reload Catalog button to check if updated/new modules are available or not.