I have RTFM but and even that damn book e-Frontier convinced me to buy... but could someone explain me the perrenial dumb end-user  the following Render settings and good practice for their settings?

Irradiance cachng
Pixel Sample
Min shading rate
Max bucket size
Min displacement bounds
Remove backfacing polys

Likewise I could use advise with nodes I never see used such as Clay and Skin.