Hi BorodMorod,
Our internal iPhone 5s is set to OS 7, and cannot be upgraded for testing purposes. I checked the historical FPS data for it, and it’s been consistently at about 30 FPS for Sun Temple since April. So there’s no way I’m going to be able to accurate internally reproduce what you’re seeing on your device. At this point, I am going to close this as resolved as the previews are not a finished product and should not be used for any sort of predictions of how FPS data is going to play out.
When the official release drops and you do further testing, we can reopen this issue if you are still seeing performance drops.
Thanks.