I understand what G-sync/Freesync does and that variable framerate should feel smoother with it, but do you still notice it when framerate is fluctuating from let's say 60-90 FPS, or 90-120 FPS, ...and more importantly - is it distracting? Does locking framerate to some flat amount provide better experience in terms of not noticing spikes/slowdowns in framerate?
The main purpose of GSync/Freesync is precisely to prevent you from noticing such fluctuations (which you usually notice by sudden lag spikes). In addition adaptive sync prevents screen tearing from framerates higher than native refresh rates of the monitor.
Within the adapative sync enabled area (usually 30Hz+) the tech is active and you won't be able to notice even sudden frame drops.