Straight or drop? If you go for drop handlebars (We love them!) they provide lots of possible positions. You’ll spend most of your time riding on the hoods, a comfortable position with wrists straight and elbows soft, and you can also lower yourself by moving hands to the lower or forward part of the drops to make yourself more aerodynamic when battling headwinds or taking full advantage of exhilerating down hills. If you do go for straight (flat) handlebars, add bar ends that allow at least one other possible hand/body position.
If you want drop bars for touring, but are concerned about reaching the brakes quickly when commuting, look for a bike that has cross-levers, or ask the bike shop to add some. These are a second set of brake levers mounted on the top section of drop handlebars. But very short cross-levers are of limited use, since moving your hands so close to the midline puts you in an unstable position.
On very long trips we have found BG Bar Phat pads, placed under the wrapping of the handle bar, to be essential for not suffering from repetitive stain type injuries due to vibrations originating from rough road surfaces. This product is made by Specialized.