If I understand well; you can have an SSS with a beveled or smooth edge, and adjust that edge with a folowing color adjust shader. I use that option a lot. Also when I make image maps, I can later adjust river widths or paths with it. But for a simple shape it's the same, as long as it's a gradient. If you set bevel to 99%, and have it followed by a color adjust with gamma set to 0.01 you end up with a very thin line.
