Resolution downscale control quality and performance.
Blur Iteration does not make big difference.
Scatter Distance and Scatter Intensity makes Big Difference,
Soft Depth Bias you should not change, its only required if you change character scale.
SSS Map is using current Diffuse map as input(if not using any map, then its look different) and that's why Subdermal Scatter Color has less effect.
Color Affect Direct can make it more effective but i dot recommend it.
I will add Decal Map as SSS Map input in next release so user can manually control which part should have what effect.