If he constantly came across as the brilliant, strong, utterly incisive person that is below the surface, I think it would freak people out. And he knows that. So he just lets them think he's kind of a whacko.

Yes! Totally!

The light and the dark-- both sutras, together. It's implied that it's unusual for a sanzo to hold both, and interesting that Genjo Sanzo's apparently the heir to them both as well.