i can answer one of those questions, now I'm assuming when you say 6th string your talking about the high E, and pinch harmonics are about placement mainly, hitting the string in a differnent place produces and different harmonic. But you must hold the tip the pick(better with thicker picks) very close to your thumb and as your pick hits the string, your thumb should hit the string as well, thus producing a pinch harmonic. I wish there was a better way for me to explain it, but also, different tunings can provide different harmonics. Zakk Wylde does his legendary pinch harmonics in D flat or C usually, but when in standard tuning, its not too easy to pull those off. It just takes practice, Im sorry I can't explain it as well as I wish I could, I hope this helps a little bit though.