Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Collision Type
GV_COLLISION_TYPEParameter: Use Deformed Points
GV_COLLISION_USE_DEFORMEDParameter: Matrix Mode
GV_COLLISION_MODEParameter: Include Children
GV_COLLISION_USE_HIERARCHYParameter: Selection Tag 1
GV_COLLISION_SELECTION1Parameter: Selection Tag 2
GV_COLLISION_SELECTION2Parameter: Tolerance
GV_COLLISION_INPUT_TOLERANCEParameter: Collision
GV_COLLISION_OUTPUTParameter: Distance
GV_COLLISION_OUTPUT_DISTANCEParameter: Polygon Index 1
GV_COLLISION_OUTPUT_INDEX1Parameter: Polygon Index 2
GV_COLLISION_OUTPUT_INDEX2Parameter: Point 1
GV_COLLISION_OUTPUT_POINT1Parameter: Point 2
GV_COLLISION_OUTPUT_POINT2