I've just recently bought an ASUS XG32VQ (1440p, 144hz, Freesync) for my RX 480 8 GB. I've noticed strange behaviour when in 144hz mode; it flickers heavily when I use it for general task (browsing, scrolling, idling in desktop), both with Freesync on and off. However, when I game, no flickers to be seen. When I set to 120hz mode, the flicker is completely gone.
Already DDU-ing,reinstalling graphic drivers to latest (18.3.4) and installing monitor's driver. So far I can't eliminate that non-gaming flickers.