For Plex:
In YouTube download-material settings: Extra-> check “generate nfo files”
In plex, create a library called “YouTube” or whatever you’d like, category set to “other videos”. Use scanner: “Plex Video Files Scanner” set agent to “Personal Media.”
Under Plex settings “Agents” make sure under both the “movies” and “shows” tabs that the “personal media” agent is set to use “Local Media Assets” and that that is top priority.
Plex will use the nfo files generated by ytdl for metadata.
I believe there is a dedicated YouTube series agent, but those can be finicky. This way, ytdl has already done all the metadata work.
Yeah, it won’t. Only Plex’s own screengrabs.