Speaking a bit for the US here (though even that is a patchwork of different rules), there are very few cases where a cycleway is compulsory for bicycles and forbids other transportation methods. Usually the only implied forbidding is motor_vehicle. Everything else is generally allowed, though there may be different right of way expectations.
So when I’m mapping here, I follow the recommendation that @emvee noted, and interpret bicycle=designated to mean that the way is designed for bicycles, and bicycles are expected to be the primary user. This is stronger than “yes” because in a common law community you can ride bicycles nearly anywhere, but some routes are preferred because they were built for bicycles.
So to map this to the German case, the official blue traffic sign is the highest form of designated and it is backed by law. This is very uncommon in the US - if we followed this convention there would be almost no use of designated here for bicycles (or horse or foot, for that matter).
For the “case 2”, clearly identifiable as a cycleway, but not compulsory, then I’d ignore the law for the moment and focus on the intent. This would map in the US to something like this 36 Bikeway where I live - it is 27km long, wide, signed for bicycles, named for bicycles, etc. You could walk on it or ride a skateboard or crawl on your hands and knees, but the intent is clearly bicycles. In your case, because of the above convention about designated implying no for everything else, you’d want to then add the various yes's for foot, horse, etc.