if you delete an app from the home screen, is it completely deleted? Or does it lie in some kind of dormat state?

Usually you will get two pop ups you have to answer. One for deleting and one asking if you want to keep the data or delete. Not all apps do this but most have for me. The app will remain available for redownload in the App Store with a cloud indicator that you already “purchased” it unless it is removed from the App Store for some reason in the future.

deleting it from the Home Screen does not delete it from the device. Go to settings>general>iPhone storage>select the app>select delete.