Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Collision Type
GV_COLLISION_TYPE
Parameter: Use Deformed Points
GV_COLLISION_USE_DEFORMED
Parameter: Matrix Mode
GV_COLLISION_MODE
Parameter: Include Children
GV_COLLISION_USE_HIERARCHY
Parameter: Selection Tag 1
GV_COLLISION_SELECTION1
Parameter: Selection Tag 2
GV_COLLISION_SELECTION2
Parameter: Tolerance
GV_COLLISION_INPUT_TOLERANCE
Parameter: Collision
GV_COLLISION_OUTPUT
Parameter: Distance
GV_COLLISION_OUTPUT_DISTANCE
Parameter: Polygon Index 1
GV_COLLISION_OUTPUT_INDEX1
Parameter: Polygon Index 2
GV_COLLISION_OUTPUT_INDEX2
Parameter: Point 1
GV_COLLISION_OUTPUT_POINT1
Parameter: Point 2
GV_COLLISION_OUTPUT_POINT2