Does that help with "auto"play & PIP thats triggered by scrolling? I have not managed to completely deactivate PIP videos in Firefox settings/about:config.
I keep running into autoplayed videos in Firefox even with all the relevant settings turned up to 11. My solution to this is for the entire website to go straight into the DNS blocklist. TrashCrunch is one of those sites, and for even better reasons than just obnoxious ads.
you've tried setting media.videocontrols.picture-in-picture.enabled to false? it seems to be enough for me, although about:support still shows "Picture-In-Picture" Add-on (of type app-builtin-addons) enabled.