In order to add a scene into the VSE with a scene strip, you'll have to make a new scene for the VSE contents, as shown in this gif(from this post: https://blender.stackexchange.com/a/184931/37272):
To render from the VSE you'll need to check this box:
What you want to do is quite easy to do in blender with motion tracking.
Open a new project as VFX File > New > VFX
In the Clip Editor (not the Video Sequence Editor) open the video you want to use.
Add a tracker on the face or whatever feature you want to track.
Track the element.
In the solve tab of the tools window, in the geometry section use &...
I have just downloaded video into Twitter with next rendering settings. On the picture below I marked significant properties. Some of them can be set with other values according Twitter documentation I guess. For example fps can be till 40.
In my case it looks like the problem was in audio codec. I did not have any sound so the codec was none. But Twitter ...
The UI of the Speed Strips are super unintuitive. I've tried to address the subject matter here without any success: https://developer.blender.org/D6110
There are four ways to change the speed of the strip, using the speed strip options. I hope listing them here will help you and others out:
"Stretch to input strip length"
The "Use as Speed&...