Yes you can cluster devices. I have a NAS in addition to the my laptop proxmox cluster. It lets me use the NAS as storage, so the VMs/lxc’s virtual disks are actually on the NAS. This allows me to make the VM/LXCs Highly Available. So if one laptop crashes it’ll automatically spin up the things running on that laptop on a different one. This can also be done with ceph, but I already had the NAS, so ceph seemed redundant.