Hey @SamTe
Generally speaking, users install a “Virtual TrueNAS” when they are looking to use their existing hypervisor (ProxMox, XCP-NG, VMware) for the compute portion, and leverage the NAS/SAN functionality of TrueNAS only. They install TrueNAS as a VM so that they can get all of the ZFS functionality and management, and present storage from TrueNAS in a “loopback” style to the host again.
There are some caveats to it, but a properly-configured virtual setup can be very close to the performance of a dedicated unit:
Of course, the other solution is to install TrueNAS bare-metal, and use its built-in virtualization and containerization functions (which will be made even more capable in the future) to run your workloads.
Different strokes for different folks. 