Radeon boost and other Radeon kexts do device property injection. WEG can force load the falcon SMU firmware as described in the docs:
Various patches necessary for certain ATI/AMD/Intel/Nvidia GPUs - acidanthera/WhateverGreen
github.com
It can also be done directly in Opencore without using any kexts. This is what I'm using for Radeon VII including my own powerplay table in Opencore that provides the same performance as the RB kext. "Radeon VII PowerPlay Table Generator" can't be linked here but its googleable if you want to roll your own.
...