Assuming you’ve already created a video feed, once you grab a video embed from GrabPress > Video Feeds > Select Videos, you should be prompted to enter a size for your video player. The minimum size we allow is 300×250 (min size supported by our player). That should be small enough to fit on mobile devices, as most devices have higher resolutions now.
The player size options should also appear in the edit post > search for GrabPress videos (icon) workflow, as well as the GrabPress > Catalog search workflow.
In our next version, we’d like to also add the option for a responsive layout (player size will adjust to 100% width of DIV). However even when we add that feature, the player will still have a minimum width of 300 px wide.
I hope this answers your question, let us know if you need anything else.