Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Matrix Mode
GV_SPLINE_MODE
Parameter: Use Uniform Distribution
GV_SPLINE_USE_NATURAL
Parameter: Use All Segments
GV_SPLINE_ALL_SEGMENTS
Parameter: Offset
GV_SPLINE_INPUT_POINT
Parameter: Segment
GV_SPLINE_INPUT_SEGMENT
Parameter: Position
GV_SPLINE_OUTPUT_POSITION
Parameter: Tangent
GV_SPLINE_OUTPUT_TANGENT
Parameter: Length
GV_SPLINE_OUTPUT_LENGTH
Parameter: Closed
GV_SPLINE_OUTPUT_IS_CLOSED
Parameter: Segments
GV_SPLINE_OUTPUT_SEGMENTS