I'm still learning about Wisteria myself, so I can't answer most of your questions with any real certainty. But that said, I think you would be fine to twine the stems, if that's what you want to do.

I'm learning about how to train them into a Tree form, as I'm thinking of trying it. Often those stems are twined around each other - sometimes using more than one variety/color to make an even more interesting and lovely show when they flower. They grow together like this, eventually forming a self-supporting "trunk". There are many pictures on Google Images. The vines seem to gain strength from this rather than harm.

They seem very vigorous and hardy vines, tough to kill.