This is my first experience with zfs. So far I've been okay with the Proxmox UI, but I also haven't tried anything other than vanilla VMs. I've enjoyed using Proxmox and learning it, but it also seems like an extra layer that I'm going to have to keep updated and maintained.
I might expand storage, but as it is, I'm doubling my current available storage, I have enough offsite backup capacity for a long time, and I'll have the original 4tb external HDD if I want to shuck it. The main issue is getting all my data centralized with as little duplication as possible.