On the carbon bar front I think it may have a lot to do with how you hold your grips. I have a friend who tends to ride with a bit of a death grip and the carbon one up bars relieved his wrist pains. I've never had any wrist pain riding and I can't notice the difference with his bars. I can feel a lot of other things but bar compliance is not one of them! I tend to ride with a fairly loose grip though (maybe from being used to 80-90 psi tires on a bmx).
I currently have DT350 18T and Bontrager 108T Rapid Drive. I like the 18T because it's quiet and works just fine for me in all situations and had zero problems with weird shore tech instances. I think maybe it depends on your riding style, I think I am just constantly aware of the position of my cranks relative to the terrain unconsciously? I find the biggest difference is the noise to which I prefer not having. All my friends absolutely love angry bees so I am the weirdo.
I can give you a specific example in my case. I have run DHR II/DHF 27.5" in 2.8, 2.6 and 2.4 (exo casings) on 30mm and 40mm rims.
I am a certified lightweight (sub 150 lbs) hence the EXO casings; but I can definitely notice the difference so I imagine that would be magnified for a heavier rider. All of these tire widths feel good on 40mm rims, only the 2.4's feel good on the 30mm rims. This is mostly North Shore riding but also includes jumps and other reckless riding. Hopefully that helps your decision.
I borrowed my friend's Slash and had a similar experience. For him it allows him to be able to ride the same trails and keep up as he is less experienced of a rider. For me that bike gets me into all kinds of trouble, overshooting corners and landings because of the increased speed; if I go slower on it though it's not as fun as my 27.5 remedy. (Both bikes are sized M/L and the remedy is significantly shorter reach)