Those are settings for the videocard driver. What you do there can affect all software which uses the videocard. This might be handy in certain situations, but it's not necessary.
Games, such as Fortnite, have their own settings that allow you to fine tune the game's performance. Usually you find these settings in the game's 'options' menu. There's usually a 'video' or 'graphics' submenu there, and that's where you can change this stuff.
What settings you should use depends on what card you have, which you did not say.