Mainstream NASs (like Synology and QNAP) are very good at what they’re built for, which is be available on the network and have plenty of storage.
They CAN do more, but then you start to notice the limitations. It is still “just a NAS.” It’s not called a NASAHVAVMM (Network Attached Storage and Hypervisor and VM Manager)
If you want to do what you described, a smaller NAS would probably be good for backups, but look into a fully fledged, capable server too.