If you want to keep HAOS as the OS (and the nice update/backup experience), there's a middle option nobody's mentioned yet: run the extra apps as add-ons instead of a separate Docker setup. There are community add-on repositories (alexbelgium's is the big one) that package Sonarr, Radarr, Prowlarr, qBittorrent/Deluge and Jellyfin as HA add-ons, so they live inside the Supervisor's containers and get included in HA backups if you want.

A few caveats for your plan:

• Do the SSD move first. Torrenting plus a media library on a 256 GB SD card will wear it out and make HA itself slow, and HAOS on a Pi 5 boots fine from NVMe or USB SSD.
• The Pi 5 dropped the hardware H.264 encoder the Pi 4 had, so Jellyfin transcoding is pure CPU. As iBlessi said, it's fine for direct play to one device; avoid anything that forces a transcode.
• Keep media on a separate drive or share mounted through HA's Storage settings, so a full HA backup doesn't try to include your library.

HAOS doesn't really share. It's a full Linux distribution designed to be the entire OS on whatever it's installed on, and it runs its own internal containers through the Supervisor. The Supervised install, the old middle route, is no longer supported (its end of support was release 2025.12).

So on one Pi 5 you pick. Keep HAOS and live with what runs as an app there, which is what add-ons are called now. Or put a regular Linux install with Docker on it and run the official Home Assistant Container image next to the arr stack, Deluge and Jellyfin. That's the whole trade. Container has no Supervisor, no apps and no one-click updates, so anything you run as an add-on today becomes its own container, and Thread and Z-Wave, which run as apps, get no out-of-the-box support. Either way, take the full backup first, as uten151 says, and I'd do the SSD move soon: Home Assistant's own database writes can wear out an SD card.

My advice: buy the SSD now and download the latest HA image for Pi5 and save it to the SSD. Save a full backup of your current HA into an accessible network share or to a large enough capacity USB Drive. Shut down your current HA. Power up the Pi5 with the SSD, configure the fresh instance of HA on the PI5 (name, IP Address, etc. to match your HA instance). Restore the backup.