60hz, 60 fps aren´t really smooth enough lol, so you could state too that something less that 165hz+ is not smooth haha.
60hz and you convert the spare Hz to 90 in sliders and setting to ultra could be the better choice with a 4090. MR is really horrible, though better than a stutter fest, if there isn´t other chance, ok, use it like I did for several months. Now I am in very smooth and some stutter from time to time or bad sceneries like to watch a film of 24hz, no problem, better than MR for me and 60Hz.