We measured FPS with The Witcher 3: Wild Hunt game, in Full HD, WQHD, 4K and with the graphics quality set to the highest allowed level.

The frame rate recorded with the GeForce GTX 1080 Ti is 92fps for Full HD, 87fps for WQHD and 51fps for 4K. The difference with the GeForce GTX 1080 is about 2%, 30% and 34% for the aformentioned resolutions, respectively.

Notice that even GeForce GTX 1080 Ti can not maintain 60fps under 4K and the highest rendering quality.

In the Watch Dogs 2 game we set the video quality to "maximum" and measured the frame rates in various resolutions.

Watch Dogs 2 poses a high GPU load under high quality settings, and it also requires high multithreaded performance from the CPU.

As a result, both the 1080 and 1080Ti GPUs reached the maximum frame rate of about 60 fps in Full HD, and their difference in WQHD was very small at about 7%.

At 4K resolution, the frame rate of both GPUs was lower than the 60 fps. The GeForce GTX 1080 Ti recorded 44.3fps and the GeForce GTX 1080 gave 35.3fps.

Given the capabilities of GeForce GTX 1080 Ti, it seems likely that the GPU can maintain 60 fps or more under WQHD, as long as you combine the GPU with a CPUs with high multithreading performance. If you want a comfortable Watch Dogs 2 play, you'd better get a 6-core CPU at least - up to 12 threads.