Hi Jeff,
Thanks for giving Post Notif a try!
Yes, subscribers should be able to choose the categories they wish to subscribe to, but that is (currently) only available to them via the initial confirmation process and, subsequently, via the preferences link they’ll receive with each post notification email. As for why there are no options shown on the confirmation page, please check that you’ve selected the categories you wish to be available to your subscribers (via: Settings >> Post Notif >> Category Settings).
As to your second question, because there is no assumption made by the plugin that a subscriber is also a known user of your blog (i.e., has an account that they actually sign in to on your blog), the widget is hidden only when a subscriber visits one of the Post Notif-generated pages (i.e., confirm subscription or manage preferences). Integrating the plugin’s functionality with known users is something I’ve considered but have not chosen to implement to this point. Honestly, it opens a can of worms, with added complexity (both functionality and code-wise) that I am not convinced is worthwhile. I suspect some of the other post notification plugins out in the directory probably provide this though, so I encourage you to look around if it is essential for your situation.
Thanks,
Devon