ninja edit: THIS IS FOR PC GUY
AA can be controlled by Scalability. Perhaps this is what is happening?
You can put something like this in your scalability ini
If you then call r.MSAACount=1 you can toggle between Temporal and MSAA, and use scalability to set the level.
Its great here on Vive. These settings may not be 100% though.
My personal favorite setting is just MSAA of 2x and r.screenpercentage 160
That will give you nice looking UMG and 3D.
I find it runs better than 4x MSAA at 140 percent…