Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Strength
FP_BLEND_OBJECT_GLOBAL_STRENGTHParameter: Radius
FP_BLEND_OBJECT_RADIUSParameter: Distance Falloff
FP_BLEND_OBJECT_DISTANCEFALLOFFParameter: Blending
FP_BLEND_OBJECT_BLEND_MODEParameter: Excluded Group(s)
FP_BLEND_EXCLUDED_GROUPParameter: Create Group
FP_BLEND_EXCLUDED_GROUP_CREATEParameter: Strength
FP_BLEND_OBJECT_RANDOM_STRENGTHParameter: Scale
FP_BLEND_OBJECT_RANDOM_SCALEParameter: Frequency
FP_BLEND_OBJECT_RANDOM_FREQUENCY