Inside edge wear is the result of incorrect alignment. Based on the number of alignments I've had done to my cars and the before and after numbers toe is the culprit.
One of these days when I have the time I need to scan in some of these so I can post and show the numbers.
Outside edge tire wear while I can't recall ever having this occur on the rear tires has occurred on the front tires once on my 06 GTO (lousy chain tire store alignment) and my 996. In the case of the 996 the wear was not severe but it was noticeable. The cause was incorrect toe. The result of bumping the front tires against a low curb/sidewalk when pulling into a dark hotel parking late one night way past my bedtime.
The uneven wear took thousands of miles to manifest itself but the howling that the tires emitted took under 1K miles to appear. OH I remember now I didn't drive the car but maybe 3K miles until I had the alignment touched up. I could not stand the noise. The noise subsided and tire life was not much affected by the front tires still wore more on the outside edges than any other areas and they have before and since always worn evenly. Part of the reason was the tech told me with the tires already worn down and unevenly the alignment outcome might not be as good as it would be with new tires. I accepted this because I was willing to risk it to gain some quiet. Afterwards the car felt a bit strange, but not intolerably so and after awhile as the tires worn in a bit from the alignment the noise subsided and the car felt ok.
In the case of the GTO I do not recall any noise and I do not recall how soon I noticed the wear but since the fronts were due to be replaced along with the rears next time the rears needed doing I just ignored the wear.
Anyhow, these cars have a range of alignment settings that are acceptable. Different dealers (ignoring the one indy I've relied upon) have different philosophies. In one case one tech aligned my car and when I got the car back it felt a bit weird. When I took it back he told me he had aligned it that way to ease tire wear on my long trips/drives. I thanked him but asked him to give the car a standard out of the box vanilla alignment. He redid it and the car felt better. Tire life has always been acceptable with a proper alignment so I saw no need to compromise on car feel for the sake of a few more miles of tire life.
At other dealers the alignment is more aggressive to give the car I guess a tighter feel. But this can have the toe set in quite a bit and this can lead to shorter tire life, with the inner edges going in some cases in under 10K miles.
Always my advice is to get the car aligned by a shop that knows these cars. The guidelines are full tank of gas, car empty of junk (weight), spare tire/tool kit/jack (whatever the car came with) properly secured. Some shops use ballast to add weight to make up for the driver not being in the car others do not. Porsche AFAIK does not say to use any ballast. Oh and in one recent posting someone posted he sat in the car while it was aligned. Anyhow, I've had cars aligned with the weight, and without (mostly without) and I can't tell the difference and tire life was unaffected.
Now as to whether you want a mild sort of alignment or a more aggressive one I can't answer that. I know I prefer a car that feels connected to the road that doesn't wander about doesn't have a vague feel to the steering yet delivers given my style of driving easy 15K and up to 23K miles with even tire wear across the front tires' tread faces and across the rear tires' tread faces.
I will add that the best alignments, the ones that had me loving the car's feel while at the same time had the tires lasting forever (so to speak) the printout of the alignment graphic had the setting lines of each setting box right on the smallest hash mark in the center of the setting box.