My expectation for the first version will be a working navigation that guides you along your route (including rerouting, voice, etc.). Especially for manual actions like POIs, changing the route etc. you might have to fall back to your smartphone.
In the long term, we might add more features like adding fuel stations during the navigation, but this is out of scope for the first version. If you look at the Android Auto version, this is roughly the scope we are looking for a first CarPlay version as well.