For me, flat bars are too limiting in hand/arm positioning. I can no longer do traditional style drop bars, hence, I have a couple of alternative handle bars that allow a lot of hand movement and room for accessories. A drop bar that has become my favorite all around bar is the Ritchey Beacon, reach 65mm, drop 80mm, and 36 degree flare. I was at first a bit surprised by how much I liked them, with the exception of the width toward the drop ends. I have gotten used to that and these bars have helped with badly arthritic thumbs, and chronic spinal and shoulder issues. I can still get fairly aero when riding into a headwind, and I can stay there for an extended time. Weight and price are reasonable, comfort factor is really high.
Another option I like, sort of an alt bar, the Velo-Orange Porteur bar, and I use mine with the 15 degree rise instead of drop. Sort of a short reach, mild curve mustache bar. I am using this bar with an 11 speed drivetrain: 6400 bar end levers in friction mode, cross type brake levers, and 11 speed rear cassette, 11-34, and 6500 short rear derailleur. A more upright position, using a longer stem due to shape of bar, grip area and 25.4 clamp. Another versatile, lot of room for movement, very high comfort level. It is a bit limiting with component compatibility and how they are set up. The bar end levers work great for me.

I just saw Maelochs post, he gives great advice. It is not just about the handlebars. Making changes in small increments and keeping track of them, I found to be a big help. That includes detail on what was done, what was liked or disliked.