How do I permanently delete content from applets

If you are referring to the Up Next queue list (instead of the Library), then shows can be removed from Up Next one at a time, or else everything at once. Note that this is an account property that will be applied to all your devices with that same Apple ID account.

To remove an item from Up Next, click-and-hold a tile from the Up Next row in the TV app on Apple TV box, until the contextual menu pops up with an option to Remove that item.

To reset all of the watch history including the Up Next list, use the Clear Play History option (Settings﹥Apps﹥TV﹥).

Follow the steps in the support document you posted from.

Delete movies and TV shows in the Apple TV app

This will delete any downloads you have.

However your purchase history cannot be altered. You will always have access to whatever you have purchased.