As an idea, I use an SSD as a "Default Download Directory" within qBittorrent itself, and then qB automatically moves it to a HDD when the download is fully finished. I do this because I want the write to be sequential going into my ZFS pool, since ZFS has no defragmentation capabilities.
Hardlinks are only important if you want to continue seeding the media in its original form and also have a cleaned-up/renamed copy in your Jellyfin library. If you're going to continue to seed from the HDD, it doesn't matter that the initial download is done on the SSD. The *arr stack will make the hardlink only after the download is finished.