1. Can't comment much here since I'm using the Job Integrated which is a dac/pre/power combined into one! Though I do encounter more differences with my cord into the Job than for example, a cord into power conditioner.
2. In my own experience, a cord with thicker gauge often sounds fuller with more body and bass. Some do sound overly thick and congested, but the good ones often don't. Similar to Watchdog, thin cables didn't work out too well with me.
3. Not that I'm able to tell. I've heard silver cords that sound warm and full, and copper cords that sound bright and harsh, so now I don't really care what construction or material a cord is made out of, only whether it works in my system or not.
4. Have not had the chance to test longer cords vs shorter cords of the same model, but the default length for most of my cords are 5-6 feet.