Frame Generation Latency: NVIDIA DLSS 3 vs AMD FSR 3 vs Reflex Integration: Advanced Implementation and Real-World Architecture

I’ve been running controlled latency tests across DLSS 3, FSR 3, and native rendering in competitive titles like Valorant and CS2, and I’m hitting some confusing numbers. With FSR 3’s frame generation, the input-to-photon delay seems to creep up significantly compared to DLSS 3’s implementation—am I measuring this correctly, or is my test methodology flawed? Specifically, how much of that latency penalty is the optical flow interpolation buffer itself versus the injected frames not receiving fresh input samples? And does anyone have hard data on how much Reflex actually recovers when FSR 3 FG is active, since I’ve read that FSR 3’s approach handles the latency compensation differently under the hood?

More importantly, I’m trying to understand the UI decoupling mechanism—when you navigate menus with frame generation on, does the interpolated output lag behind the actual UI input, or does the system detect non-game content and bypass interpolation? In fast-tick-rate shooters, even menu input stutter matters for my reaction timing. Has anyone dug into the engine-level hooks, like how Unreal’s frame delivery pipeline or the DirectX 11 vs 12 paths affect this? I’m particularly interested in whether the latency cost is consistent across both APIs or if one stack handles the interpolation queue more efficiently.