facegen Facegen data files and NPC_ subrecords

[elderscrollerr 0]

In which cases files 'meshes\actors\character\facegendata\facegeom\xxxx' and 'textures\actors\character\facegendata\facetint\xxxx' are not needs or needs? Which subrecords ('Head Parts', 'QNAM - Texture lighting', 'NAM9 - Face morph', 'NAMA - Face parts', 'Tint Layers' ...) must be not empty if npc needs for facegen-data files? In Skyrim, Skyrim SE and Oblivion.