Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Height
PRIM_FIGURE_HEIGHTParameter: Segments
PRIM_FIGURE_SUBParameter: Legacy Axis Mode
PRIM_FIGURE_LEGACY_AXIS_MODEParameter: Switch to Updated Figure
PRIM_FIGURE_SWITCH_TO_UPDATED