I tried using the ZWO native driver in SGP126.96.36.199, it allows the control of gain and offset, but the e-gain logged in the FITS header always give a value of 3.6.
Using the ASI generic ASCOM driver has the e-gain value logged according to the setting.
Also, it looks the CCD temperature is just logged with the ASI ASCOM driver.
Attached please find the 2 FITS files for reference, one captured with the ASI ASCOM driver with gain = 270, another one is with ZWO native driver with gain = 270.
2 files captured with ASI ASCOM and ZWO native driver