The misgender animation only lasts 18 frames, you are inactionable for the first 9, so you need to perfectly input on frame 10-11, 12 is already too late. Use CC to avoid knockback & dmg in case you miss your frame, to protect yourself while you master this technique.
That does not affect buffer frames unfortunately, it’s just a visual setting. With it off you just get “more frames per frame”; the game would be broken if your video settings affected your input timings. Just keep practicing, it works!