Thanks for the feedback Yossi. To answer the last question first, the way to do that is to use the Bella Sheet material, and add scattering. Regarding the different types, we have discussions ongoing here about which to keep or get rid of (e.g. Urethane). The three new materials are these:
This is specifically for use with a texture set like you get from the various PBR sites, or like you may bake out of a tool like Substance Designer/Player.
This is much like the Arnold Standard Surface material, and has been requested & is being developed with input from friends of ours in VFX. This is why it has so many settings. We are continuing to work on this, putting less-used parameters in their own sections, below the main ones.
This is intended as a simplified version of the Uber material, and provides just the most impactful/useful parameters of the Uber.
Regarding your comments about ease of assignment, I have not forgotten your prior requests to make some dedicated shelf commands for this, and your further comments/impressions above will be useful when I do that. I am also thinking of something similar to what you mention, where the Uber/Principled materials get a drop-down at the top of them, or a button that shows a list, where you are able to select some named types like you mention (glass, etc), and we set the material up according to what you choose.
Lastly, I should mention there is still missing a related function for Uber & Principled, where you can choose a PBR texture set, and have all its textures instantly assigned where they should logically go in the material.