Unity and OpenVR games have fantastic VR mirror views that are non distorted and scalable. Some games even support different camera angles.
Anything regarding mirroring is badly documented and there are no real workarounds that provide a meaningful solution besides the mirror mode ( not working with the vive and its restricted to the HMD aspec ).
Hope we can get an ETA on this, i dont understand why this is not a priority in the current streaming age.