Setting "stretched resolutions" (like 1024x768) directly in the config file to lower the GPU load.
Forcing "Alpha Performance" mode to prioritize frames over visuals. Fortnite Chapter 3 Config Pack
The "config" part usually refers to a specific GameUserSettings.ini file that players use to bypass standard in-game limits. 1. Performance "Config Packs" (FPS Boost) Fortnite Chapter 3 Config Pack
Lowering latency by disabling mouse acceleration and enabling "Nvidia Reflex Low Latency". 2. How to Manually Access Your Config File Fortnite Chapter 3 Config Pack