Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Size
MDATA_SELECTLIVE_RADIUS
Parameter: Pressure Dependent
MDATA_SELECTLIVE_RADIUS_PEN_PRESSURE
Parameter: Visible Only
MDATA_SELECTLIVE_VISIBLE
Parameter: Tolerant Selection
MDATA_SELECTLIVE_TOLERANT_EDGE