If supported by the camera, set the Read Mode property to the desired value. A value of 1 indicates High Gain mode.
Fast Exposure is an experimental features in all INDI Camera drivers. It enables client (e.g. Ekos) to take multiple exposures in a sequence without awaiting the client to request the next frame.
You can enable Fast Exposure by toggle it in the camera Options tab as shown below. You do not need to set Fast Count as it is handled automatically by Ekos.
In Ekos or App, take exposure as you normally would. For example, if you add a Job with 5 exposures, without Fast Exposure it works like this:
With Fast Exposure enabled, the driver immediately starts the next exposure as soon as the image data is downloaded from the camera.
Therefore, the camera is always busy exposing and downloading data without any wasted time setting as IDLE.
It's right there! Check under Diffraction Limited manufacturer and you should see the SBIG drivers.