Panniers for Dahon or my own set up?

Currently have the Dahon mu d10 with stock rack. I'm setting off for a 6 week bike trip in Europe (airbnb and credit card style, no true bike-packing). I currently have the Deuter Transit 40L and am considering rigging it to the seat and rack with a bolt-style set up. Wondering if anyone has had luck with the Tern Big Mouth Panniers (23l each).

I'd like to have one-bag-travel, so I can easily put it on my back to catch a bus or a train. I plan to avoid bad weather with public transit. So I'll really only have one hand for the bike, and the other hand for the bag(s).

Any wise input here is much appreciated!