UE5 - How to improve UE5 FPS? It is too low... clamped or slow motion, even with a new GeForce RTX 3080

Start out by resetting the FPS smoothing to its default values. This just fixes screen tearing, more on that here. After that, you’re going to want to see if your problem is the fps limit (by default 60), by running t.MaxFPS through the console to uncap it.