They go where they’re needed. My research led videos go into DEVONthink, quite often after compression by Handbrake. For teaching I actually re-upload to Vimeo, the better to control the experience and to ensure future access, as well as to remove advertisements. These end up embedded in Notion pages which I use for teaching. The few entertainment videos go into my raid.
As regards organisation i treat like other files. There’s no iTunes or Plex like approach. I re-title them according to my needs and use DEVONthink’s groups.