Gain setting for a QHY 533C camera

Long exposures (>=300s), unity gain. Short exposures (<=180s), 60. In between, your choice, depending on the subject.

Unfortunately I don't have the SkyX so I can't tell. The best thing is to get a proper analysis of the performance using SharpCap, the result of which would tell you what gain value will be unity gain and what gain would given the drop off in readout noise (60 gain units refers to that condition). Remember that offset and gain correlate in inverse manner and for NB imaging (assuming you would use dual-band filters) you might want to push more on gain if you're after the faintest stuff.