There are a lot of factors that go into optimal width. Rider size, bike geometry, conditions you ride and much more. What is conformable for you might be very uncomfortable for me, and that can vary from bike to bike.

I ride 44cm road bars on my drop bar bikes I like them wide as I have wide shoulders, a 55cm albatross bar on my city bike, and 60+ cm flats or risers on my mountain bikes. On those bikes and in those riding positions and the conditions i use them in they all feel right to me, but might not to you.

I think manufacturers of flat or riser bars tend to make them wide and let the end user go after it with a pipe cutter. That way they can offer fewer widths and let people dial them in. It's personal preference. Cut it until it feels right, and then it's right.