Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Hull Value
METABALLOBJECT_THRESHOLDParameter: Subdivision Viewport
METABALLOBJECT_SUBEDITORParameter: Subdivision Renderer
METABALLOBJECT_SUBRAYParameter: Exponential Falloff
METABALLOBJECT_EXPONENTIALParameter: Accurate Normals
METABALLOBJECT_ACCURATENORMALS