Whether the shim is over or under, doesn't make a difference on noise - it couldn't. There is no difference, the same stuff is between the cam and the valve stem, they're just reversed.
More noise can come from different cams though - I think the higher lifts and longer durations cause more cam chain noise, but I don't have anyhting excessive that I'm worried about. I upped the idle from 1400 to 1700 because the higher cam lift favors it more. This got rid of low idle chain slap.