Here is one way. Note these are just steps and you will need to adjust and tweak at each step.
Create a keyframed bezier mask around the object.
Duplicate the track as a standalone (not a reference).
Invert and blur one of the masks to make the mask appear slightly larger than the object. You can zoom in slightly on the mask (optional). Zooming in will cause the over mask to get larger but will cause issues with any cutouts. The examples didn't bother with cutouts so it would not be an issue.
You can slightly blur the original mask to get the fade-in and fade-out effect.(optional)
Composite the 2 masks together. This should give you an animated 'halo' mask around the subject.
Overlay a solid color or pattern onto the 'halo' mask and add to the original video.