Liquids move. Much better to split them up into 1 liter/quart quantities and spread them around in bottles on the frame. If you have to carry 5G in the back, spread them over several 2 qt bottles and spread the weight. The front panniers are to improve the handling; the weight in front, especially if it's low, helps the bike track better in a straight line. Not really an issue but it is nice on a long trip especially if you have a converted road bike. Watch out for heel strike on rear panniers. If you have big dogs (12 or so) it's common. Wind resistance is not an issue on such a heavy bike setup with 200+ lb of rider plus bike usually. Studies have shown that under 15mph or so, drag is not such a big deal. Rolling resistance either, so fat tires are ok as long as they are reasonably smooth for the road surface you are on. In touring, convenience and durability wins over weight and aerodynamics, up to a point. Read some of the journals in crazyguyonabike.com and pay special attention to the equipment lists.

Recumbents are a different story; the rider position makes climbin a pain in the behind so any little bit helps. That's why so many have specially set up luggage distribution and fairings. The reward comes in the ergonomics and flat-land speed. So, it's all about the fit between the equipment and the mission at hand.

By the way, not everyone needs to spend 500 dollars plus on Ortlieb panniers. Jandd, Eastpack, REI and others have good enough panniers for weekend trips and you can find them used at reasonable prices. That way you can test things out before deciding you are a fully-supported guy/gal rather than a credit card or light packing person instead.