Start by confirming whether you actually need a concealed system or just the sanitaryware — if you’re only replacing a wall-hung toilet within an existing frame, you may not need to touch the Duofix or Omega frame at all. But if you’re planning wall work from scratch, decide on the frame first, since it determines what flush plate options and sanitaryware will fit, not the other way around.
If you’re deciding where to buy, prioritise finding a genuine authorised dealer over chasing the lowest price. Frame height, depth, and compatibility with your wall construction need to be confirmed against your actual bathroom — something worth doing in person rather than trusting a listing page, especially since a wrong choice here is expensive to correct once the wall is closed up.