I found this:
https://www.qhyccd.com/index.php?m=c...94&id=55&cut=1
Scroll down about half way under "QHY linearity test".
So the different modes have to do with the speed of driver timing. I thought it might be the same as FLI cameras where you have a choice of digitization rates with the slower ones taking longer to download but have lower read noise (but as far as I know this does not affect full well depth).
To be practical though, you'd have to settle on one mode for all use or at most one for LRGB and one for Narrowband otherwise it will become a complicated mess trying to manage the files with different sets of calibration files needed.
Its bad enough with exposure length, gain and offset plus different temperatures as variables compared to CCD where its only exposure length temperature. Plus in the case of FLI digitization speed.