Hey Peter, good question! For a 4K film, I'd recommend just using the high poly version without doing the whole normal map thing. This does mean that you'll need to attach all mesh details instead of letting them float above the surface. I'd also recommend using 8 or 16k textures instead. Good luck!
Thanks. I'm going to enroll on the yearly subscription as I'm going a video project that we want to drop by March 2020 and I will need your help and the help of the community to pull off what I'm trying to do. See you soon.