Air was chosen to implement VR off the back of initial trials on the ride in 2015, which was done out of hours, as part of a project by Figment Productions - this was a favour that Merlin allowed them to do in return for discounted rates on their previous and future collaborations.
The concept of VR on Air materialising, in my opinion, was due to the convenience of already having half a prototype system built on the ride.
Back to SW8 - it has 3 trains which are sit down. I can assure everyone there is nothing unique about the trains other than they have little pieces of wood (like banboo, weirdly) stuck to the side of them in a nice finish.