PTT on weak side shoulder, routed up plate carrier shoulder wire retainer on weak side, inside shoulder, close to neck, down the side of hydration carrier on plate carrier on weak side, to radio on weak side cummerbund, routed with wire routed inside cummerbund. Headset plugs straight down into PTT.
Since the sling goes under the weak side arm, you only have the section of sling on your back that can rub and that is mostly just on the hydration carrier. I have been meaning to get some nylon strips with velcro to wrap the wire in as a chaffe guard so I can molle it to the side of the plate carrier back or side of hydration bladder, but not gotten around to it. I have had several wire jacket separations that I have had to repair from rub or connection points on the wire, but that is mostly from using a coiled wire connection from my Peltor PTT to radio, which is weak, instead of a straight wire.
Most guys I know who run an earpiece run it under their clothes.