As I mentioned in the other thread:
The latest 8KX and 8K+ firmwares (with 120/110Hz) are not yet released because we are currently testing them together with the panel vendors, to make sure the refreshrates are 100% stable without ghosting or other abnormalities. I suspect we will release it upon the days 8KX first batch starts to ship.
The refreshrates changes are always made in firmwares. PiTool automatically shows available refreshrates that are allowed by the firmware.