The coming update is still in its beta phase, so there is no documentation available yet. You can find manuals and videos about the integration of Studio One, because DAW Mode was inventend for the CS18AI and then integrated to the Series III consoles. This is different with the HUI/MCU emulations, which were developed for the Series II consoles and are now being implemented to the CS18AI. You can find two documents describing the features on the download pages of the Series III caonsoles. Look for the two manuals listed below:
https://www.presonus.com/products/StudioLive-32/downloads
StudioLiveā¢ Series III StudioLive Series III HUI Emulation for ProTools DAW Control Addendum
StudioLiveā¢ Series III StudioLive Series III MCU Emulation for Logic DAW Control Addendum
There is no emulation available for Reaper, but there should be some basic functions. DAW Mode for Studio One is far more extended.