Sure! The subscribeWithOptions API method allows you to mix subscription types.
This means you can easily subscribe a channel with guaranteed message delivery (by setting a subscriberId) while signalling that you also want to send the messages as push notifications (to alert users that are using your app).
The guaranteed delivery mode is great for in-app messages, so messages are not lost if the device reconnects for some reason. Push notifications are great to alert a user that is not using your app.
Use both subscription types to get the best of both worlds.