Upright is good but the bikes of that style I've ridden long distances on tend to be not very efficient - your center of mass if well rearward of the bottom bracket. What worked best for me is a bike with a tall stem so that the bars can be at or above seat level, with multiple hand positions. A trekking bar or a traditional road bike bar has lots of positions and if you can get one of those placed high enough you may want to do that instead of a traditional omafiets or beach cruiser type bike. For me anyway it's a lot more comfortable, especially into a headwind.