We have both of these already, don't we? When I go to settings I see Interface Language which I assume is the website itself, and then a whole list of languages below it which I assume are post languages. Those assumptions could be wrong as I'm new here, but that's what they seem to indicate to me.
Below that you have Type and Sort Type, and selecting these will make it your default feed view. This one I know works because I've experimented with it a bit myself. If you always want to see popular posts from all of your subscribed communities set it to Subscribed and Hot and it will stay that way by default.
I suppose it does make sense to have undetermined because people might not make a selection in that box at all when posting and without the undetermined option set, you'd not see it. It should probably be the default though, like a setting that is always on. That would prevent having to make the selection and potentially even making an undetermined post by accident.