I have multiple nic assignments both physical and virtual for my Nethserver installs and you can see how I deploy them here. For my Xen based hypervisors I run everything on them from Windows 10 machines, Pfsense, Nethserver, FreeNas (with very specific conditions) and so forth. As @Andy_Wismer (someone I consider as a local Proxmox guru) would note though, the XCP-NG does not offer any docker like setup.