<p>I have not been to southern France, but I have been to Venice and Paris couple of times each. My most favorite combo is the 24-70mm with a D300. On occasions I have taken the 70-200mm along, I have never used it,. More often than not the 70-200 stayed in the hotel locker, along with the flash and tele converters, to keep the backpack light.<br>
<br />As for a backpack, if I do not take a lot of equipment, my favorite is LowePro Orion Trekker, mainly because it is light and has served me very well over many years. Recently, I have taken the <a href="http://www.amazon.com/Kata-KT-PL-3N1-35-Light-Backpack/dp/B005IQGN66">Kata 3-N-1-35 Pro Light</a>. The bag is not light, but I would not classify it as heavy either. It holds a lot of equipment, and is very flexible, but more you put in it the heavier it gets of course. The real nice thing about this bag is that it can be configured either as a backpack or a sling. As you said, a sling is not comfortable over a long period. With this bag even in the backpack configuration, you take the strap off one shoulder, and the other side serves as a sling with secure flaps on either side, so you do not have to put the bag down to take the camera and/or accessories out.</p>
<p>In the end I am getting more and more tired of carrying heavy cameras during travel, pretty soon I am getting a Fuji X-E2 :-).</p>