Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Open Magic Bullet Looks...
VP_MAGICBULLETLOOKS_LOOKSBUILDER
Parameter: Preview
VP_MAGICBULLETLOOKS_PREVIEWAFTER
Parameter: Mix
VP_MAGICBULLETLOOKS_STRENGTH
Parameter: Save Preview
VP_MAGICBULLETLOOKS_SAVEPREVIEW