i think the suspension is not the weak point of the E9X M3. its actually very good for progressive rate. the EDC shocks are really sharp. by far, the brakes are the weakest point of this car and its heft. in order to really be quick you have to be confident and the one aspect if any you want to be 110% confident in on the car is the brakes.
as far as a verified setting for triple adjustable suspension i don't believe it for a second. i'm sure you friend is running a very different tire from you and the car might even be more rigid and certainly a good deal lighter. so unless you built the same car and have the exact same line then his suspension setting is not going mean anything. the only way to get tangible results is to test drive the car and taking measurements that prove the shock settings are in fact improving usable grip and resulting in higher corner entry and higher exit speed. i think even then a lot of that can be in your head. just by thinking the car is more capable you are more confident and push harder. its the placebo affect.
the shock settings are also only part of the equation with coilovers. the biggest effect i see on usable grip is the spring rate. for one thing progressives are a compromise. too soft initially and possibly too firm when fully loaded. i think a linear spring is far more useful. however you get into a very long drawn out process of picking the right compression rate of the spring for the car and the particular track. this is why most manufactures just make more settings on shocks and stick to a progressive rate spring.
in my personal experience with an E46 M3. i had TC Kline dual adjustable coil overs. one of my best friends at the time also had the same car same tires and same suspension. we would spend quite a bit of time after a lap with a log book of settings we tried and lap times and we narrowed down what our preferred settings were. my settings were completely opposite of my friends and our lap times were within a second of each other. looking back now, i think if i just went to little firmer springs on the E46 i think i would have had the exact same time again without wasting $3000 and half my day writing down settings.
"It gave you amazing satisfaction, but anyone who says he loved it is either a liar or he wasn't going fast enough." - Jackie Stewart on racing at the Nurburgring