Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Radius
MDATA_SELECTLIVE_RADIUSParameter: Pressure Dependent Radius
MDATA_SELECTLIVE_RADIUS_PEN_PRESSUREParameter: Only Select Visible Elements
MDATA_SELECTLIVE_VISIBLEParameter: Tolerant Edge/Polygon Selection
MDATA_SELECTLIVE_TOLERANT_EDGEParameter: Mode
MDATA_SELECTLIVE_MODEParameter: Mode
MDATA_VERTEXPAINT_MODEParameter: Strength
MDATA_VERTEXPAINT_STRENGTHParameter: Pressure Dependent Radius
MDATA_VERTEXPAINT_RADIUS_PEN_PRESSUREParameter: Pressure Dependent Strength
MDATA_VERTEXPAINT_STRENGTH_PEN_PRESSURE