Ah yes, you're right, detectedframes does nothing, max frames ahead does something, presumably constrains the video processing stuff. Anyway, as of now since using the latest beta patch those entries have been removed. Running the non-beta version re-entered them, so I really don't think will be required in the future. Personally I did not really notice any performance change with those values, I just read that a few other people said they increased performance.
Increasing the FOV makes the game far more enjoyable for me as it gives you much better awareness/perception. Along with that it does slightly increase framerate, you can notice this better when using + and - on your numpad to zoom in and out then looking around.