Hope I can be of assistance with the VR side of things -
We started using Enscape a few weeks ago on the HTC Vive virtual reality headset and are still amazed with the results within both Revit and Sketchup. Rendering is relatively fast and the VR option is simple plug and play as in - just install it then switch on your VR headset (Either Oculus or HTC Vive) and the controls will be available in the overhead tool bars. There is a trial on their website if you want to give it a go.
You can ALSO produce a VR walk-through using Unity 3D - however this is dependent on the geometric size of your model - Polygon count is big deal in any game engine - you cant just bring in a huge plant room full of geometry and expect the engine to perform, there is significant optimization you can do in either 3DS Max or Blender to bring the count down. Textures are also a topic on their own and achieving the overall look of the simulation is also dependent on your skill level within Unity. Major areas to play with would be lighting and UV wrapping. This is however the cheapest option as Unity is free and has a very big knowledge base on their website to learn from.