I've rebuilt my Wordpress blog and it is now responsive, so when you resize your browser all photos, etc. will scale accordingly. There are plugins to do this with embedded Youtube videos, but Youtube will no longer default to HD unless you have a ridiculous screen resolution. Worse, when you go full screen on an iPad it will stay at the default 360p or 480p playback with no option for the user to change it.

I would like to use Smugmug videos instead, but the embedding has radically changed recently with next to no options anymore. I can't find a way to embed a Smugmug video on my Wordpress blog that will responsively scale. Also, I'd like it to default to HD even when viewed at 480px because my timelapses of the night sky with stars can't even be seen unless it plays back at HD, even at smaller resolutions. This would also resolve the issue with iPads playing full screen at pathetically low resolution like Youtube is doing.

Any suggestions on a plugin or method to make this happen?

The video size can only be selected by the visitor viewing the video if our Flash player (not available on iPad) is used. To my knowledge it is not possible to change the default size the embed is playing back.
You could add a suggestion to the SmugMug feedback pages.
That way other users can vote and comment on your suggestion, and it helps us keep track of all suggestions made.