Finally finished setting up and testing a Peertube instance. The video stuff and object storage related things certainly make it more involved than other fediverse software, but overall it is working quite nicely. Just need to find some workable solution to using GPU acceleration in containers, but I think I mostly figured it out (might work after a server restart, but my sweet, sweet uptime makes me procrastinate on that 😅 ).
Not automatically, but you can configure it to mirror certain video channels or individual videos. But I have not looked into that too much yet.
As for storage: a typical video you would find on such a platform with the different stored video resolutions and so on will take between 0.5 and 3 GB… depending on the length and how well it compresses.