So I found out that the adaptive pixel density feature has been replaced with the new dynamic resolution system from Epic (r.DynamicRes.OperationMode). However, this only works with Temporal antialiasing and TAAU enabled. In theory that is, as I have yet to manage to get the new system working. Currently, when I enable it both left and right eye displays become disconnected from each other (one up to the right and the other down to the left), and the views become zoomed in. Also, headtracking stops working.