Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Format
AIIMPORTFILTER_FORMATParameter: Connect Splines
AIIMPORTFILTER_CONNECTSPLINESParameter: Group Splines
AIIMPORTFILTER_GROUPSPLINESParameter: Create Vector Object
AIIMPORTFILTER_CREATE_VECTOROBJECTParameter: Force PDF
AIIMPORTFILTER_FORCE_PDFParameter: Greedy Fill
AIIMPORTFILTER_GREEDY_FILL