UI stutter (Nvidia+Xorg)

I am experiencing an intermittent lag in the UI.

Examples:

when I type something in the terminal, sometimes there would be a delay between the time I press a keyboard button, and when the character is displayed;
if I focus the search field in Nautilus, the cursor will blink inconsistently, sometimes missing a blink, sometimes blinking twice quickly;
clicking the calendar in the tray, brings up the popup with a slight delay;
sometimes, switching between tab views (for example in Settings), will cause the views to flicker between one another;
some application animations, for example opening the settings sidebar in Telegram, is very choppy;
in some views, such as Nautilus/Settings, doing a single scroll up/down on the mouse wheel, scrolls the view with a noticeable delay;
typing in LibreOffice accentuates the problem, as printing on the screen lags behind a lot.

Mitigation attempts:

Disabled Sync to VBlank in both Nvidia & Compiz settings (doesn't help)
Forced Compiz refresh rate to higher value (doesn't help)
Set power profile to "High Performance" (doesn't help)
Set Nvidia card profile to "Performance" (doesn't help)
Running glxgears in the background -helps!- there seems to be no input lag, an animations are smooth

Observations:

Some applications don't seem to be affected by this stutter. For example, Google Chrome is smooth. JetBrains/VSCode the editors are smooth, but expanding/collapsing a folder sometimes has a short delay.

Here's a couple videos I took to show what I mean:

Specs:

Seems to be related to:

Edited Dec 04, 2020 by Dragoș Mocrii