The GeForce Experience is nice to get the latest GPU driver but if you use the game optimizer you find it sets the game for max eye candy and not performance as in FPS or lag.

De-installing will not change the game settings back so here I use the GeForce Experience so my GPU driver is current and know about the game optimizer issue.

To get the game performance back you usually have to learn what game settings matter. This changes from game to game so I can't be specific since again, changes with game, PC and if online, your connection. So pick a game then google like this: https://www.google.com/search?q=Optimizing+Fortnite&gl=US