I got a bike fit a few years ago on my gravel/cx rig and the fitter recommended trying a wider bar - I splurged on an Enve G series carbon handlebar to replace the OEM aluminum one and it turned out to be one of the best bike purchases I've ever made. It fits better, rides smoother and has the fringe added benefit of shaving a few grams. I'll leave it up to others to argue if that is a result of the material (carbon vs alloy) or some other design aspect, but I have zero regrets on this purchase and would not hesitate to buy another one. The difference between this bar and my stock alloy bar is very clear.

Also for the OP - I have been running my carbon handlebar on an alloy stem with no issues. The Enve bar has a grippy material where the stem clamp goes, which (I think) negates the need for carbon paste.