If you can, choose a knee wall of at least 1.40m. That makes the rooms much more spacious and nicer!
We have 1m everywhere. In the bedroom, we built up to 1.40m with drywall, so the bed is not so far under the slope. And what can I say, after living in it for 6 months, I would actually prefer to have 1.40m everywhere. For us, it was not possible because of the requirement for a single-story building.