Actually, Gears 4 does NOT do 4k at 60fps. If you choose Visual (4k) mode, you are locked at 30 - and it is BEAUTIFUL. You can also choose Performance mode which locks you in at 60 with HDR and enhanced visuals, but it is at 1080p. Still looks a LOT better than even on the One S. I had the GoW4 One S and just upgraded to the 1X - and the 1X is AWESOME!!!!!
Forza is 4k at 60.
Every game will have different enhancements depending on what the developer wants - but they all play better. CoD WWII is stunning with silky smooth gameplay on the 1X.