BigBlueToe

There should be plenty of room in the Bob for everything you want to take. Adding front panniers would be fine, but you'd be adding some wind resistance. That big yellow bag is waterproof, like a dry sack used for canoeing. I didn't need any waterproof bags (like on my sleeping bag) when I put everything in the big yellow bag. Just do a little planning so that the stuff you're most likely to use during the day on top. It's a big bag, and if you have to rummage around in it for something, it can take awhile.

I also carried a handlebar bag. Despite the wind resistance, I felt it was worth it for the convenience. That's where I carry my wallet, keys, camera, maps, and snack.

I didn't feel much effect on handling with the Bob. In fact, when I started from a rest stop I often had to look in the mirror to make sure it was hooked on. The hardest part was maneuvering it in the campsite, store parking lot, etc. - walking speed when I had to turn sharply. It can tip and put a lot of stress on the bike frame.

Having said all of that, I've tried both panniers and the Bob and I prefer panniers - not by a huge margin, but it's a solid preference.