Anita, in my zone 7a garden I prune all my clematis in late December. Fall is generally not a good time to prune since the clematis will more than likely still be actively growing and pruning will stimulate more growth. This is not what you want to happen when colder weather is set to arrive.

As to your second question, some of the cut vines may fall off in the winter wind but some may stay and require removal by you. It all really depends how much you are planning to cut off, how much you leave on the plants, and how windy and turbulent your winter weather is.

Anita, there is someone in our zone who has Clems growing up her arborvitaes. She is going to post pictures as they get growing later this season. I can't remember her name. I prune in February. I find type 3's vines really easy to pull down. They are brittle and break up easily. Not sure how easy it would be if they were less dried out though.