Remove or delete apps from iPhone
You can easily remove or delete apps from your iPhone. If you change your mind, you can download the apps again later (if they’re still available in the App Store).
Do any of the following:
* Remove an app from the Home Screen: Touch and hold the app on the Home Screen, tap Remove App, then tap Remove from Home Screen to keep it in App Library, or tap Delete App to delete it from iPhone.
* Delete an app from App Library and Home Screen: Touch and hold the app in App Library, tap Delete App, then tap Delete. (See Find your apps in App Library.)
If you change your mind, you can redownload apps you’ve removed.
This is from Remove or delete apps from iPhone - Apple Support (CA)
Like they say, you can change your mind, but I'm not sure about what happens to any user data or files that were created by the deleted app.
In fact, any app that you've ever downloaded and deleted will forever haunt you by way of showing up with a download icon next to it,
... unless you start with a new Apple ID.
Oh. My answer was at the bottom of that same page:
Note: When you remove a built-in app from your Home Screen, you also remove any related user data and configuration files. Removing built-in apps from your Home Screen can also affect other system functionality.