I've had a proxmox machine running for about a year now, and just set up a standalone Frankenstein NAS running truenas scale (only because I was having trouble with HBA firmware on truenas core)
If you're new to zfs, truenas is an easier entrypoint because its GUI is easier to understand. Proxmox has been rough for me, and I'm often jumping into the cli to manually do things that I think should be easy to do in the GUI but aren't.
That said, proxmox is more full-featured and (I think) more stable and lightweight than truenas scale. If you're comfortable with zfs, or learning how to manage it via cli, then I think proxmox is a better workhorse.
Long-term, though, do you foresee expanding storage? A single 8TB hdd seems unlikely to fit your needs for very long.