If you want to use panniers, you can't use that rack. You'll need a rack with side supports. I didn't google the Tubus model you ordered, but they make excellent racks. It's going to fit your bike, don't worry. If the bike comes without rack mounts and the salesman assured you that it would have them, refuse delivery. Or get an Old Man Mountain rack, or a backpack, or... You'll have options. There are solutions to every problem.

If you don't really need panniers, Ortlieb makes nice backpacks with that roll top design. I've never used an Ortlieb bag but they are popular with messengers. The roll top closure is similar to what I've seen on bags designed for kayakers. Bags that are made to stay dry even if you flip your boat, which is why I think it really is a very waterproof closure.

The Orlieb packpacks are kinda huge, but better too big than too small and you never know when you'll need to do some shopping on the way home from work. A little extra capacity never hurts.