Same here, got a TrueNAS running for storage with no services, and a Proxmox box next to it that uses the NAS for storage. Solid setup.
What made you less confident in TrueNAS? I’ve been running it for a few years now, not 1 hiccup in all that time. Granted, I never ran any other services on that box.
For me it’s all NFS. I have storage mounted on proxmox for VMs, ISOs, backups, … I use full VMs instead of LXC, so I have direct mounts of the shares inside the VMs if they need it.