As I understand it, which I’m not sure I do, the -arrs will automatically grab torrents. In my mind, this would eat up a TB pretty quickly.
You seem to be partly misunderstanding. They only grab what you tell them to, so they won’t automatically fill your disks with random videos.
What they do is grab any movies or TV series that you specify, and give you the option to upgrade them to a file size and quality limit that you set. For example, you could tell them that movies can be a maximum of 10GB per file, and TV can be a maximum of 3GB, and that you’d prefer 4k.
There are profile options that let you grab any available copy of a video, and upgrade it as better versions come along.