The facial morphs/blendshapes are all exported to Unity automatically. There is nothing for you to do. Polygon reduction is also automatic for the figure/body (manual process for clothes/hair/accessories). Daz to CC3 Base via Transformer puts your naked model at ~27K triangles with Game Eyes & teeth. Conversion from CC3 Base to Game Base gets you down to ~10K. LOD allows you to go much lower, but there is a problem...
General for Unreal Engine & Unity- Added: Mouth open is now a FBX export option. Jaw, lower teeth and tongue bone animations can now bake into morph targets.
- Limitation: InstaLOD Merge Material function is incompatible and not permitted with FBX export option Mouth Open as Morph enabled.
This means that the teeth will not be linked to the Mouth Open blendshapes, so you will see a mouth full of teeth any time the character opens the mouth to speak. I don't know anything about animation yet, so I don't know how to link the teeth mesh Transform to blendshape sliders. If someone can provide direction on this it would be helpful...