Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Generate
MGMATRIXOBJECT_MODEParameter: Draw Size
MGMATRIXOBJECT_DRAWSIZEParameter: TP Group
MGMATRIXOBJECT_PARTICLE_GROUPParameter: Follow
MGMATRIXOBJECT_PARTICLE_BLENDFOLLOWParameter: Constrain
MGMATRIXOBJECT_PARTICLE_BLENDDIRECTParameter: Particle Priority
MGMATRIXOBJECT_TPPRIORITY