Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Strength
FP_BLEND_OBJECT_GLOBAL_STRENGTH
Parameter: Radius
FP_BLEND_OBJECT_RADIUS
Parameter: Distance Falloff
FP_BLEND_OBJECT_DISTANCEFALLOFF
Parameter: Blending
FP_BLEND_OBJECT_BLEND_MODE
Parameter: Excluded Group(s)
FP_BLEND_EXCLUDED_GROUP
Parameter: Create Group
FP_BLEND_EXCLUDED_GROUP_CREATE
Parameter: Strength
FP_BLEND_OBJECT_RANDOM_STRENGTH
Parameter: Scale
FP_BLEND_OBJECT_RANDOM_SCALE
Parameter: Frequency
FP_BLEND_OBJECT_RANDOM_FREQUENCY