Correction. I guess it is a bit different than a seedbox (I've never used a seedbox)
Here is what I found online:
A Debrid service has support for multiple premium file hosts, while a Seedbox does not
A Debrid service, once it completes a torrent download, will stop seeding, while a Seedbox seeds a download forever until you stop it from seeding (hence the name).
Some Debrid services, such as Premiumize, can seed for a certain amount of time.
A Debrid service is usually cheaper than a Seedbox.
RealDebrid not only allows you to download but also stream directly from them. I use rclone to mount the drive to my media server and read the files with Plex/Jellyfin.
Yes! Plex_Debrid is the automation component that will go and add the torrents to RealDebrid based on your Watchlist in Plex. The Plex_Debrid Github has a step by step guide on setting each component up.