online video causing lag, but not low fps

[henkkrakers]

specs:
1070ti
1700x
144hz 1440p monitor for games
2x 60hz 1080p monitors for video/other things.

while playing games on my 144hz monitor and watching a video on my 60hz monitor at the same time. my game would stay at 180-220fps but my game would start feeling laggy/stuttery/slower. I've had this problem on two seperate pc's and can't figure out why it's happening or how to fix it. I have thought of a few things i might be able to do but would prefer to hear my options from smarter people. (my ideas were 1, virtual machine this pc, 2. use two pc's with synergy program, i haven't tried these things yet).

any ideas on how to fix this problem?

 

[ikaz]

Have you checked your CPU and memory usage via task manager when this happens.

 

[henkkrakers]

Have you checked your CPU and memory usage via task manager when this happens.

30% cpu usage and 50% memory usage (16gb ram total)