Not every game is affected. Just try for yourself leaving the FPS uncapped and check if the game has frame pacing issues like stutter, tearing or extreme input lag. Normally when the game does not reach your monitor limits without AFMF, then you don’t need to limit it. Remember that AFMF frames are interpolated, and do not come from the game engine rendering pipeline.
It doubles but the frames generated by the game are the ones that matter to your refresh rate, no the interpolated/afmf ones.
If the game without frame gen max out at 165fps, then enabling AFMF to double the frames (330fps) you give you a smoother experience. Try it!