To add, there is something about those old 40s and 50s era technical films like you linked that is just so... I don't what exactly it is, but I find them fascinating and genuinely informative, even though they are explaining tech that is decades obsolete.
It's pretty awesome that they are still available 70+ years later in excellent quality!
Or just run both, period!
Plex is definitely more straightforward to maintain remote access to your content (including library sharing with friends & family). So it may be worth keeping up for that aspect alone, even if you end up liking Jellyfin better.