NOPASSTHROUGH should be set to 1 (active) because the CyberStorm PPC does not have a pass-through port for Amiga modes.
KEEPAMIGAVIDEO is your choice, IIRC if you disable it (set it to 0) the Amiga output will be blanked when a CyberGraphX screen is being shown. In general I would say if you have a monitor connected to your Amiga output and another to your graphics cards set this to 1 so the second monitor stays active otherwise set it to 0.
HTH
Robert
