Proxmox + TrueNAS Scale VM

I'm about to setup a new Proxmox server (having never done it before). I'd like to run TrueNAS Scale in a VM so I can replace an old QNAP NAS (TS253A). My question is would it be better to setup Proxmox first and then create a TrueNAS Scale VM or can I baremetal a TrueNAS Scale install, install proxmox and then virtualize the TrueNAS install?