Are the video thumbnails only sizable by changing the number of items per row? My issue is that the thumbs are too high. For me the titles are far more important than the thumbnail because I am only doing embed videos.
If it is predominantly videos, you could change the thumbnail size so they are a different aspect ratio. The thumbnails, by default, are 300 x 300 so they will appear as squares. If you changed that to be 384 x 216 (which is a fairly standard for videos 16:9 ratio) then they would appear similar to this:
After changing the option, you need to rebuild the thumbnails.