Advice please

Finally got blown plaster done and rest of wall was skimmed. Now its dried Im now sanding, filling and sanding (you get my drift) - not planning on having a border around room at top of window level so just wonderin if anyone has papered up to the top of the window level as opposed to a few inches under where a border would be? If paper should go lower then do I need to cut out plaster? Hoping this makes sense to you all, have attached a pic to help ☺
Thanks in advance
Ange