Hi Elliot,
We appreciate your comments on Editor X and welcome you on this journey with us.
We looked into your site and your images and we able to identify why there are differences.
In the Classic Editor, the container holding the video is a Strip. The video was added as part of a strip background, so the video is stretched to fill the space.
In Editor X, you are using a VideoBox component. The VideoBox is set to always fit the video without changing it’s aspect ratio. If the component has a different aspect ratio as the video file, then there may be blank space around to fill the container.
As an alternative we recommend that you use GIF files instead, our team is aware of the missing capability to add videos as a background and are working on some solutions.
Please let us know if you have any questions regarding this.
Thanks,