I have a question for any Tumblr users

I don't post videos very often on Tumblr at all- Usually I just use freeze frames from a video. However, on the occasion when I do have a video to post, I usually use an iFrame to embed it, hosting the video itself on my site. I create a dedicated html page on my server where the video will display at 100% width, with no margin or padding or anything. I then embed this page as an iframe on Tumblr, this seems to work just fine, but I haven't really checked how it is handled on mobile either.

Hey, I've messed around with this some and the take away I got from it is this. There isn't a way to effectively embed videos from sites that it doesn't already support.

Additionally on blogs that I have gone ahead and uploaded videos to, their reblogs, follows and likes are significantly less than on blogs that focus on gifs in the same niches.

If it fits with what you're trying to do, I would recommend instead turning the vids into gifs (pornhub has an online tool to do this for vids hosted with them if I remember correctly) and then post those with a link back to the source video. An upside to this is Tumblr blogs that have original gifs, as in ones with your own watermark and clips that haven't been seen elsewhere gain new followers, reblogs and likes much, much, much faster.

You are right about gifs. I have much more success with gifs. You can use these gif generators:
pornhub.com/gifgenerator
giffio.com

I didn't know about giffio.com thanks!!!

It is one of the gfy's members site.