Even though it's early code, the Xbox One X build we played runs almost flawlessly for regular missions at a straight 30fps, regardless of rendering mode. However, there is one exceptional area in the Gamecom build that causes issues. The Ghasghor siege is a large-scale battle that buckles Xbox One X's performance to around the low-20s. It's a mission with a surplus of enemies and effects, and the bottleneck applies whether you're on quality or resolution mode.
As a stress-test it's fascinating to see the standard Xbox One's adaptive v-sync used here, causing occasional screen-tear. Also curious is that the quality mode appears to push Xbox One X harder, compared to the resolution mode - creating a divide of 2-3 frames per second in matching scenes. Interestingly, engaging dynamic resolution makes no difference here, and it may be the case that the sheer number of entities is causing the console to be CPU-bound.