I spent a decent amount of time making a nice web application to wrap up the functionalities of yt-dlp, makes it really easy to follow content through Jellyfin!
Have a look if you have the chance, I think people could make good use of it: https://github.com/MattMckenzy/ToothPick
It’s meant to periodically scan the locations for new content, so yes, newly added ones will be downloaded as well. By default it scans every 10 minutes!
As for channels, it supports any web page that yt-dlp can parse as a playlist, so more than likely whatever kind of page you’re thinking of will work as well!
yt-dlp is impressively compatible.