As far as bits with true chain mouthpieces… I think some horses might prefer a well made one, if they are trained to neck rein. As far as I know, a chain mouthpiece should really only be used on a leverage bit on a horse that knows how to neck rein. If you use a snaffle you’re likely going to be direct reining
at some point, and dragging those links over tongue and bars and lips to some extent.
OP, I’m not trying to bash your bit choice, but I don’t see how the thickness of a bit is going to help it be softer if there’s a slow twist. Those sharp ridges are going to be sharp whether the bit is fat or thin. And a fatter bit with a slow twist might be more harsh than a thinner one due to the fact that it’s fatter and hitting more areas of the mouth.