AngWay there's no definitive answer encompassing all apps that one can give you.
Some apps have issues if they are not installed by Play Store but work fine after it's uninstalled; other apps you can delete the Play Store but you still need Play Services: other apps you need both Play Store and Play services; and some apps you don't need either.
Play Services is necessary for apps that use Google Firebase to deliver notifications (which don't allow alternative notification providers like Unified Push, Web Socket, etc.)