WalterT I’m confused by the gain numbers meaning different things also.
If you want low read noise, choose gain of 100. This is the gain where ZWO first triggers the Sony sensor's HCG (high conversion gain) mode.
If you want more dynamic range, use a gain of 0 (0 dB).
All other gain values make zero sense when this camera is used for DSO.
Gains between 1 and 99 will just give lower dynamic range than gain of 0, with no real change in read noise.
Gains above 101 also does not make sense, because read noise is already extremely low with HCG turned on with this series of Sony sensors, and you just lose dynamic range with the higher gains.