I own 3 devices with the X20. A Chuwi Hi 9 Air, Vernee Apollo Lite and a Sharp Z2. The Vernee and Sharp can absolutly hang with Snapdragon 820 but get handly beaten by Kirin 950 and Exynos 8890 when it comes to everyday performance. The Chuwi Hi 9 Air though is often slow as molassis. Overall, very mixed bag.
And yeah, forget gaming - GPU is really underpowered.