There are Lions Clubs in Germany too. They are very active (at least our local ones are). I doubt if they have the green bottle system, though.
What 3 words is fine, but here the words are German and I often wonder if that would be any good to a foreigner, and could lead to misunderstandings through wrong pronunciation - this would also apply in other countries as the words are always presumably in the vernacular. I once looked up my address on w3w but I've forgotten it. Delivery drivers are not usually German and can hardly speak the language, so I can't imagine it would be much use here. Also there are strict rules for addressing properties and navigation is fairly straightforward. If you're out in the sticks - say, in the woods or on a heath - it may help, but both parties would have to be native speakers.