Yes. It's need information to generate frames. They are not comes from nowhere. Minimal are two frames + time to generate. If you have real 20 fps, minimal is +100ms + unknown time to process the result.

nvidia has an option to enable ULTRA LOW LATENCY mode, as well as to disable VSync. This buffs your fps and reduces input lag !!

There are also more misc (system) tweaks . .

However, in Singleplayer games it doesnt really matter . . .

yes, its kinda like how tvs did the soap opera effect of blurring image together
it needs 2 frames to make the inbetween frames

The best experience will be always be running it the old fashioned way at native resolution with fakes frames off. Don't factor fake performance into your system decisions.

To create a frame you must have 2 frames already rendered so you are always a frame or 2 behind. If your GPU renders 60 FPS (16.67ms interval) then the output to your monitor should be 16ms or 33ms slower than the actual in-game moment, unless there are more shenanigans to reduce this lag, which most likely there are.

Yeah, no, I have yet to run into that, though I've seen people speak of it.
My setup shows 7ms per frame, so unless you have a 10K polling mouse & KB, you are not likely to run into that controversy. Average input devices are way within limits not to have an effect.
If you have no problems, don't become a hypochondriac. It's not broken.

I play cyberpunk with dlss and frame generation. 144fps, amazing graphics and no input lag.

Maybe if i compared screenshots side by side and zoomed it, i would see a difference. But in normal gaming there is no difference.

It's like when they give you a diet fountain drink or light beer on accident.

frame gen is garbage on a 3080 and i turn it off in every game that has it.....the last tomb raider that had it looked bad running it......