I find it important that I am fitted and ride so that elbows are bent and hands relaxed, shoulders relaxed, and fingers loosely draped over the bar or hoods. If those conditions are met I find bar width becomes pretty forgiving. I don't obsess over it and generally have been okay with what came with the bikes. That means narrower than my shoulders.
Back in the day when I rode a lot of tight singletrack with a lot of stuff to catch a bar or brake lever on I used to cut MTB bars real short. These days not so much.