According to the document I linked:

The first requirement is that all your media files and folders be in the same file system. Everything must be contained on a single physical or virtual drive

if it’s still possible to create hardlinks between the SSD and the Mirrored HDDs, I will go that route.

I was considering using the SSD to avoid wear and tear in the HDD because of the nature of the torrent downloads. My idea was using the SSD as a temporary/cache drive for the download itself, and then only executing one transfer move to the HDD once the media is completed. Drive noise was another concern, since my NAS sits in my living room and I want to avoid hearing the drives spinning constantly.

I am using two Seagate Ironwolf HDD, which are NAS certified. Will they suffer if I use them for downloading as well as seeding?