The best results I've seen are analogous to a modern version of rotoscoping. It involves creating a fully animated 3d model of a person and then using a well trained deep fake of the actor's face in combination. Youtuber Shamook did just that with the finale of the Mandalorian season 2. ▶ this video He actually got a job with ILM out of it. The future of CGI actors will probably involve a fusion of techniques like this in order to get it right.
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