Issue With Subsurface Scattering and Scale on a Human Model I scaled down my characters to real human measurements (around 1 m 70 cm), in meters units. I found it harder to manipulate because the characters are tiny in relation to the scene.
Also the skin shader seems to works differently. The smaller the size, the higher the strength the sub scattering is for my skin shader. I don’t understand why, it causes the facial features to lose in definition.
Then the scaling down seems to make the head and hair shrink too in viewport rendering (not so sure and not as concerned about this, but curious)
What is the scale recommendation for human model? The life-size scale doesn’t seem to work well for me. Thank you for your help.
Your subsurface radius value probably needs to come down in proportion to your model's scale.  Observe the following difference in SSS radius:


With a 60m model, 1 meter between light bounces is still fairly surface level, scaling it down the light could penetrate all the way through the model.  Here's the section from the documentation:
RGB Radius
This is not in fact the radius of the subsurface scattering, but the average path length between scattering events. As the light travels through the object it bounces around then emerges from the surface at some other point. This value corresponds to the average length the light travels between each bounce. The longer the path length is, the further the light is allowed to scatter. This is the main source of a material’s perceived “scatter color.” A material like skin will have a higher red radius than green and blue. Subsurface scattering is the diffusion of light beneath the surface. You control how far the light spreads to achieve a specific result.