I've created a preset scene for this skin test as seen in the renders above with the HDRI you see here, 1 spotlight and a pointlight as a key. The idea behind the project is, getting the most realistic skin possible for portraits with no postwork while keeping rendering times under 1 hour and around 4-5k iterations.
The biggest overall render settings for all my renders in this thread have the spectral engine on, set to natural conversion intent and cie1964 observer. Then some big tone map changes, Exposure is set at 12 (11.4 for the Aisling render) Burn highlights .10, crush blacks .20, saturation I start at 2.5 and adjust to scene these are at 2.2, same with gamma, and these renders are also at 2.2. I've also made some fstop and focal point adjustments on the camera but these are primarily for texture crispness, and will vary heavily of course depending on placement.