Well, are these 2 questions?
1. I'm using magisk to replace this file.
2. The temperature while charge is around 40, I wonder if you mean playing games while charging or high temperature due to removing the file?
I found a post
http://www.miui.com/thread-13648787-1-1.html, which basically says that uses the settings:
400~600mhz for gpu
1300mhz for big core
1500mhz for small core
Or just follow the pictures even you don't understand the language. The auther claimed to have 38C temperature with hdr & high resolution.