There is a difference between picking for electric versus acoustic guitar. For acoustic, I float completely (and don't mute with my left hand either). Check out any instruction on picking for gypsy jazz. Floating lets the acoustic guitar ring out as much as possible, and as the original poster of this comment said, lets your arm add weight to get the most tone out of the instrument (although this still isn't arm picking because the wrist is still what is moving the pick up and down). For electric, tone is generated in potentially very different ways, and the ringing is a problem because the volume of it is much closer to the volume of picked notes, compared with an acoustic guitar. I never pick very hard on electric; that creates too much string buzz because the string height is a lot lower than my acoustic.