I bought panniers (Pacific *something*) with inner pockets thinking they would help keep things organized. I ended up putting stuff in plastic bags, which was better for organizing. (Mostly 1 gal and 2 gal kitchen zip-locks.) It was nice to have a defined space for spare spokes, which defy placement in plastic bags. And the interior side pocket kept my Bowshield T-9 chain lube upright. (That stuff dissolves plastic.) But other than that, the interior pockets just got in the way. I'm convinced I could have packed better with just plain panniers. Next time, I'll get panniers without pockets. One feature my panniers had that I found unexpectedly nice was the top covers. The covers themselves were a pain. But they included net bags, which were surprisingly good for drying my alternate clothes. If my next panniers don't have net bags, I'll find another way to implement that feature.
The medium Ortleib handlebar bag was good for me. It was a good trade-off between too much stuff and not enough room. Ortleib has a standard and a deluxe bag. The deluxe bag includes a few useless features and one great interior zipper pocket. The pocket is just the right for my cell phone and wallet. A couple of times I parked my bike badly and hadn't snapped the lid closed. The bike fell over and a bunch of stuff fell out. But the wallet and cell phone were safely tucked inside the zipper bag. Also, I could always find these two most important items quickly when I wanted them. The Ortleib handle bar mount is very stable. Removing the Ortleib handlebar bag is easy for when you go in a store & leave your bike outside. Replacing it is equally easy and is accompanied by a most satisfying "snap". There's no question about whether it's secured. It's just too bad about the obnoxious and mostly useless strap feature. I guess the world isn't quite perfect yet.
For a supplier, check out TheTouringStore.com. Dave has been doing this for a while. He knows what your questions will be before you do. He's very helpful, and he stands behind what he sells. He doesn't sell the panniers I selected. But he sold me my rack and handlebar bag. His advice on mounting the rack to my Trek 520 was spot-on. When I had a minor problem with the Ortleib, he had an elegant solution that worked quite well. He even gave me good advice on mounting those panniers I didn't buy from him.