You need to be more specific on what your planned use is for the bike. What does "high performance all-rounder for mostly road use" mean? When most people think of road bikes they are typically thinking of a bike that will be ridden long distances 50 to 100 miles plus per day and/or perhaps used for racing. This means a drop bar road bike. If "mostly road use" means part time on gravel and dirt trails, then you will be looking for something substantially with wide tires. If by "road use" you are talking about 10 mile or shorter commutes or grocery shopping trips, then you may be looking for something else. Please try to explain exactly what you want the bike for so that we can help you.
Also, your idea that mustache bars or flat bars provide comfort is off base IMHO. Flat bars are used on mountain bikes because they provide leverage. However, the lack of multiple hand positions makes them very uncomfortable on long rides, and if you will be riding at speed on the road then they provide no positions that will allow you to duck out of the wind. Ditto for mustache bars, which I find even more uncomfortable because I find that they force me to ride with my wrists twisted an an uncomfortable angle. Drop bars or butterfly bars provide much more versatility. There are also other bars out there like VO Crazy Bars that provide good positioning.