Been playing around and yes it does play quite nicely these days. Its been a while since I tried snaps on Pi0's, I think last time I did try it omxplayer caused some weird overlapping issues.

I've managed to get the size down quite a bit. I could probably increase a little as the video file sizes are typically smaller than the boxart! I've settled on 320x240, no sound and 10 seconds. Looks fine on the small screen, usually 10 seconds is enough to get an idea of what the game is like, and the sound can sometimes be a little rough so not an issue losing that. Also limited to 30fps as a lot were 60.

I used ffmpeg with commands: -i input.mp4 -r 30 -s 320x240 -ss 0 -to 10 -an output.mp4

mkdir trimmed for %%a in ("*.mp4") do "d:\ffmpeg\ffmpeg" -i "%%a" -r 30 -s 320x240 -ss 0 -to 10 -an "trimmed\%%a" pause

Created a little batch file and it does them pretty quickly.

Filesizes massively reduced, one collection was 572 games. scraped videos took 1.99GB! trimmed versions took just 137MB

I'm glad I asked a silly question now :)