Yes, that curve does say how ISO (sensitivity of a pixel to light) is related to Gain, for which there is a control, and so it is helpful.
This is the article that I recommend people look at:
https://astronomy-imaging-camera.com/cooled-cameras/cooled-asi-camera-setting-in-ascom-driver/
It shows tests on long and short exposures.
And then what helped me get more comfortable was to simply attach the camera to my short refractor, put it on a tripod and launch SharpCap, go through the various settings and compare the differences in gain, brightness, gamma, etc.
Last step was to activate SGP, get it to see the ZWO and the FW, set the FW up and do some imaging.
I feel like I am ready to use the camera, and all that we need now is clear skies.
Farzad