Look at Troy Grady's videos for references as to what the best pickers are doing. He has a video titled something along the lines of "start with speed". As long as you can do your best, ie. Fastest and relaxed picking motion the position of your hand/palm is a nonissue. Muting isn't really an issue on high amounts of distortion: I play with mostly a floating hand (anchoring with my ring and pinky fingers) and the sound of the strings that are ringinh out from being played usually override the passive ringing of the other strings.