Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Subdivisions
CNURBS_SUBParameter: Factor
CNURBS_FAKParameter: Limit
CNURBS_LIMITParameter: Thickness
CNURBS_DOUBLEParameter: Bulging
CNURBS_PARALLEL