For the hypervisor I recommend either Proxmox or XCP-ng. XCP-ng is technically a better hypervisor, but I personally use Proxmox because I like the UI.
For the NAS OS, I use and recommend TrueNAS Scale. You can run Docker containers on it. All this being said, I've never used Unsaid so I don't know how they compare.
Out of curiosity, why move from OMV? I was thinking about trying it out for a second NAS.