touring weight distribution
General Principles. If you have too much weight in back, the front wheel's contact on steep uphills can be a little bit light, and your odds of pinch-flatting the rear tire can increase (especially if you are running skinnier tires relative to the load), or breaking spokes, because it already carries more of your body weight than the front. If you put too much up front, low-speed maneuvering can get a little more tricky because the handlebars have so much mass/inertia, and also it will alter the handing even at other speeds in a way that may take some getting used to. For typical riding, I doubt it is going to make much difference unless the load is really uneven. Maybe 70/30 or 60/40 weight bias towards the rear is what I've done. 

Ease of Access Also A Consideration. I've found it to be more important to arrange things primarily by ease of access, with weight balance the secondary consideration.  Gear that you use only at camp goes in my front duffel or at the bottom of the panniers or seat bag. I end up using my tangle bag as a buffer space for food, an extra layer, paper maps, or whatever other stuff I need to access frequently while riding. Top of panniers for occasionally-during-the-day-access items.