I don’t know how your first concern (over current for breakers) is addressed, but I trust that the Germans, of all people, have figured it out. This technology has been in wide use over there for years. I’ve heard that over there you can buy them from local big box stores and I think even supermarkets. I doubt that Germany would allow something that would be a fire risk to proliferate like that.

Regarding your second concern (power flowing back to the circuit when it’s supposed to be unpowered) I’ve read that balcony solar systems do include circuitry so they automatically stop supplying power if they detect that there is no power being supplied by the outlet.