Hello. 3k-5k is very low poly by todays standards. Generally character meshes are the most dense in the face. If you look at the poly count for just the arm model for FPS that comes with unreal it is around 5k. You can safely get away with around 10k-12k for a full model. But dont underestimate the importance of heightmaps, not just normal maps. Using these helps give more depth to the folds of the skin,