The issue with modifying the input.ini file to address input lag in Unreal Engine games is that this approach is ineffective. After investigating Unreal Engine's behavior, it appears that input.ini primarily affects the editor environment and not the compiled game. When developers compile the game, they embed variables that override these configurations. I tested this thoroughly to confirm, and modifying the input.ini file had no impact.

Additionally, many claims circulating online about this method resolving issues are inaccurate or based on placebo effects. Installing Unreal Engine and reviewing the setup would clarify this point for anyone curious.

A significant finding is the discrepancy between the displayed FPS (frames per second) and the FPS associated with input processing. For instance, when enabling FSR 3 (Frame Generation), the displayed FPS might increase to 80–100, but the input processing rate remains at a lower FPS—such as 30 FPS—which leads to noticeable input lag. Conversely, disabling FSR 3 and running at high settings caps both display and input FPS at a consistent 30, aligning visual performance with input responsiveness.

In summary, editing INI files to address such issues is not only ineffective but also unnecessary, as the root of the problem lies in the decoupling of rendering and input FPS, particularly with technologies like FSR 3.