Automatic wallet creation by apps for new users is one of the goals of the nwc-enclaved, and it supports zaps.

The tradeoffs with Spark are that it's a new tech and quite complex and not many people can understand it. And Spark operators have to be trusted, although I'd say they should run in enclaves too. And no fees for now but they will come and hopefully will be competitive. And 'unilateral exist' is 'coming soon' at the moment. And your wallet still has to be online 24/7 to receive payments if I understand it correctly. So - pick your poison. I think it's very promising, but wouldn't bet 100% on it right now.