Hey @andy_vs , thanks for the suggestions!
At the moment, I am taking a break, I learned so much from this project that I guess I'll start from scratch on another one to avoid to repeat some of the mistakes I did. I agree with you for the jiggle. I had to damp a lot of the fat movements since I was having stability problems and I had to run the sim with low substeps value (I have a pretty solid pc build but the mesh was rather high poly and the face had a lot of muscles too).
I guess that this was the cause of the not enough strong jiggle effect in the fat pass.
Also as you said, hair played his role too. I feel like XGen is not very handy for simulations, I always have problems and I am forced to clamp the range of motion. I will try with Houdini for the hair sim next time.
Btw, your references are super inspiring and your suggestions useful. I'll keep them in mind for the future. Thanks 🙂