Hi Ron,
You need to understand the characteristics of each settings first, and then choose the suitable setting for yourself.
1.Highest Dynamic Range: set the gain at 0, the dynamic range will reach the highest(around 14 stops), and the full well is also the highest.
2.Unity Gain: set the gain at 90, the GAIN will reach 1 e-/ADU, it has lower read noise, and other parameters become moderate.
3.Lowest Read Noise: set the gain at the highest value, the read noise will come to the lowest.
In my own opinion, I'd like to use Unity Gain.
