UserControl and Page are 2 different things. A UserControl cannot inherit from a Page, it must be hosted in a page. ModuleControls are hosted in the CMSPage which is Default.aspx. See How mojoPortal Works.
NonCmsBasePage is intended as a base class for administrative pages.
A feature can have supporting pages in addition to the module control that is hosted by the cms page, but generally feature supporting pages should inherit from mojoBasePage rather than NonCmsBasePage.
Study the code for existing features that have supporting pages to learn more (ie the forums, blog have supporting pages).
Hope that helps,