We were just spontaneously at Megabad and Elmer in Cologne.
Megabad is really just as you describe.... it’s not inspiring. At Elmer, at least they have display bathrooms set up so you can better imagine the whole thing.
At Elmer, they are wholesalers. They still plan the bathrooms with you, possibly together with one of their external installer partner companies. The contract partner is the installer, so there should be no warranty issues here. However, the price will probably end up being significantly higher than at Megabad and Reuter. The warranty advantages should be worth 10-15% more to you. But I fear it will be considerably more.
We picked up brochures from Villeroy & Boch, Bette, Kaldewei and the own brand Sanibel.