In-app purchases is not available yet in the native mobile builder, but it’s being developed as we speak, as revealed at Bubble Tour and this community update about a week ago.
You can use a wrapping service to get your app to the app stores, but using the native mobile builder means it’s not needed unless you specifically want the web version of your app to be available as a downloadable app. So to clarify, a native mobile app and a web wrapper is not the same thing: a native app is built specifically for iOS and Android using native frameworks, and a web wrapper is essentially a native shell that loads your web app inside a webview (i.e. “a fullscreen web browser”).