You can run PBS baremetal or in a LXC/VM on your PVE server. But keep in mind that in case of a problem with your PVE itself you can't access your backups anymore. So you would need to do a fresh PVE install, then create a new PBS VM/LXC, import your old PBS datastore to the new PBS and only after that you will be able restore your other VMs/LXCs. So it will work but you will need o do some extra steps in case of a bigger problem.
And you might want a offsite/offline backup of your PBS datastore too. Backups on disks in the same host or another host next to it won't help much in case of ransomware, a fire, lightning strike and so on.
And later it should be possible to backup the complete PVE host to your PBS so you don't need to install PVE from scratch. But that won't work if your PBS is virtualized on your PVE.
And like I already said, PBS isn't designed to use network shares or HDDs. Everything will be split into millions of small files and HDDs or NFS are really crappy at going through millions of files each time you do a garbage collection or verify job. So it will work but really slow. Got 10Gbit NICs and doing a garbage collection of a 300GB datastore easily takes over an hour where the disks are at 100% utilizations because they can't handle the IOPS.
