Ok. I think I've discovered the answer to this. Really wish Sitefinity was a little more forthcoming with what exactly you are able to do with MVC/Angular using the Feather framework.
From what I have experienced, as of the current version of Feather:
You can use MVC/AngularJS to add/edit Page Layouts, Widgets, and Widget Designers and that is all.
To change any of the Content forms you must still use WebForms/ASCX controls. This includes any fields/selectors/etc... used on any form used to create/edit content in Sitefinity.