Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Radius
MDATA_SPLINESMOOTH_RADIUS
Parameter: Strength
MDATA_SPLINESMOOTH_STRENGTH
Parameter: Smooth
MDATA_SPLINESMOOTH_SMOOTH
Parameter: Flatten
MDATA_SPLINESMOOTH_FLATTEN
Parameter: Random
MDATA_SPLINESMOOTH_RANDOM
Parameter: Pull
MDATA_SPLINESMOOTH_PULL
Parameter: Spiral
MDATA_SPLINESMOOTH_SPIRAL
Parameter: Inflate
MDATA_SPLINESMOOTH_INFLATE
Parameter: Project
MDATA_SPLINESMOOTH_PROJECT