According to QNAP Tech support, running cameras and recording video usually is fairly system intensive and typically requires a dedicated system.
That said, today I bought a used TVS-672XT on eBay. I think I got a steal on this NAS as it includes drives totally 46 TB of storage! Anyhow, now I will have two solid NAS units for all my backup and file sharing. I will attempt to dedicate my TS-451 to recording video from my two cameras using QVRPro.