After Media changes: Regain responsivness

This is sort of a meta issue, stemming from #1809606: Video display broken (and fitvids integration) → .

I had a pretty decent workflow to gain responsiveness (using fitvids module):
Set the file display to width: 100% and height:auto and let fitvids grap .media-youtube-video to apply its magic.
This nice and easy workflow is now broken after moving a lot of stuff from Media to file entity (I guess, or was it mark-up changes in the media_yt/vimeo modules?)

1. Using height:auto now results in a fixed height of 150px (I have no idea where this is coming from btw).
2. The usage of fitvids results in a floating video display that ignores its placing and always wanders to the top of its region. Applying clear:both to .media-youtube-video repairs this. Is this coming from media_yt or fitvids module?

I liked the old workflow (or was I doing it wrong in the first place?) because it was fairly easy to do. Ideally I would like to come back to this state (i.e. make height: auto work again). At least we have to document how to get responsive media back.
Thoughts?