I think you’re getting confused due to the point at which you’re tapping the signal for metering. It sounds like you have meters set to post-panner instead of input or post-fader.
I’m not sure why you think the DAW sounds louder than the exported file? Of course with different pan laws you will balance faders differently depending on where things are in the stereo field assuming you produce an identical mix per pan law. Remember also that the default panner on stereo tracks is a balance panner which is not affected by the pan law setting.
As you can see from the images there is no difference between PT and Nuendo when the meter tap points are set at the same point and when Nuendo is set to the same pan law as PT.
