A) A standard ~20k poly mesh with approximately 150 different face and body morphs
This is the character design we are using as part of our character development.
A 20k polymesh in EU4 terms is a drop in the bucket and the nature of morph targeting is only the vertex offset data is saved and with a few issues to resolve is the more efficient approach as to the need of a large volume of NPC characters all driven on the same BP and animation channels as will as using a single skeletal rig.
As to the use of materials the general rule is the use of geometry over procedural displacement is more efficient as you a few k in morph displacement data versus the asset footprint of a 4K displacements map.