Hey DSP, this is a great question.
Just to establish: Anchoring is important, so you will have leverage for picking. Otherwise, if you try to keep your hand hovering, it will flop all over the place as you pick, as your hand rebounds from the force of hitting the strings. Plus, you'll be stablizing your hand with your larger arm muscles, trying to keep it in the air, which is using up energy. Anchoring absorbs that rebound energy and keeps your hand in one place. You'll only be using one set of muscles to hold your hand in place against the body, instead of acting like a spring in both directions. The faster you go, the more you need it.
I anchor in TWO ways, depending on which strings I'm picking.
1 - My default anchor is corner of my palm on bridge, pretty much ALWAYS muting the Low E unless I need it to ring. There are some disclaimers here with bridge anchoring because that can end up causing problems with floating tremolos. You have to have a light touch sometimes, avoiding putting pressure into it, so the notes won't all go sharp every time you pick (unless you want that crazy sound, which I am sure I have used somewhere). I use this method of anchoring for picking on strings A through high E.
2 - If I really need to pick fast with the low E string open, I will anchor my right hand fingers (middle through pinky) on the body and high E string. (This is sort of what Marty Friedman and Michael Angelo Batio do.) HOWEVER, I will very rarely let the low E string ring open when picking fast. It's just rarely called for. I can occasionally anchor on the body of the guitar if my focus is open Low E fast picking, like a tremolo. The thing to be wary of here is that if you anchor with your fingers when picking fast, there's a big chance of extra strings ringing (you will hear this all over Marty Friedman's playing). So you need to try to make up for that with left-hand muting tricks, which is not easy!
So, my answer is to use a couple of methods for anchoring and not rely on just one. It also really depends on how much gain you are using. With a clean tone you can get away with a lot less anchoring and muting. But with high gain metal and rock this becomes a real thing to focus on.
Love this question, so thank you. It made me grab my guitar and investigate.
-Carl.
Carl King[br]GuitarTricks Video Director / Producer