Keep Active: Tries to start two camera streams and keeps both of them active. Switching the active video stream is handled inside LitePlacer software. This consumes more USB bandwidth, but should solve issues that some Windows system have selecting between the supplied cameras.
Fast: Does activate/deactivate cameras, doing it efficiently (but see below). Activate this method by unselecting "Robust" checkbox.
Robust: Does activate/deactivate cameras, using a slower but supposedly, more robust method.
In theory, this is the order of preference. In practice with a reasonably modern machine, the difference is small if any. Use any method that works. The reason for the update is the "Keep Active" method.
As always, I appreciate any feedback!