Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Mode
FP_SPLINEEMITTER_SPLINE_MODEParameter: Restriction
FP_SPLINEEMITTER_SPLINE_RESTRICTIONParameter: Restriction Threshold
FP_SPLINEEMITTER_SPLINE_RESTRICTION_THRESHOLDParameter: Scatter
FP_SPLINEEMITTER_SPLINE_SCATTERParameter: Interval
FP_SPLINEEMITTER_SPLINE_INTERVALParameter: Thickness
FP_SPLINEEMITTER_SPLINE_OFFSETParameter: Thickness Variance
FP_SPLINEEMITTER_SPLINE_OFFSET_VARIANCE