In some games, such as halo mcc, cod mw2, and mw3 my refresh rate seems inconsistent while watching things on my second monitor. For example a twitch stream. If I close it, the game feels perfectly fine. I also tested with just a regular youtube video and it was fine as well.
On halo when using vsync and having no stream playing on the second monitor it is buttery smooth and at 144fps. When I put a stream on, fps dips to 100-120 and refresh rate seems well under 144hz.
Some games that work perfectly fine with streams open are CoD MW(2019), Red Dead Redemption 2, Battlefield 1, and Battlefield 4.
Main monitor: Dell d2719hgf @144hz DP
Second monitor: Acer gn246hl @60hz hdmi
cpu: ryzen 5 3600 @ 3.6ghz
ram: hyperx fury red 16gb @ 3200mhz