I saw several surgeons, one of whom advised the supraclavicular approach. He said that for his patients with venous symptoms he also makes an incision below the collarbone to take out as much behind the vein as possible. I would ask your surgeon about this.

Will you be having a post-op venogram to expand the vein if necessary?

Yes, it will be painful but if you are medicated well you should be fine. Just speak up if your pain isn't managed well.