I am testing Unity 2017 betas these days, and I found the SetResolution does not work in iOS (in Android seems to work).
I am testing in an iPhone 7 Plus (1920x1080) changing native resolution to 1334x750. The same code works perfectly in previous Unity versions like 5.5.1 or 5.5.3. I am using Metal API as first graphics option and GL2.0 as second.
The app is not frozen but it does not render anything showing a black screen. The game is in fact working because it logs in into GameCenter after some seconds (I can see the Gamecenter welcome popup), but nothing from the game itself is shown.
This is happening in Unity 2017.1.0b6 64 bit.