While I don’t have much experience using nixos as a hypervisor I do have a few years experience using Proxmox on top of Debian. Managing multiple VMs and backups are very straightforward with Proxmox. As for your daily driver VM, the skies the limit, well mostly your HDD space is the limit. I’ve realized that after trying a ton of different distros the only real difference is the package manager and the preinstalled software.