If there is any activity on my second monitor, my fps in tf2 drops down to sub 60. this can be something like watching a youtube video to just getting a steam message or someone chatting in my twitch chat. my main monitor is 144hz, secondary monitor is 60hz. this problem goes away if i only have one monitor plugged in. i have this problem with other source games as well, like cs:s and gmod.
i've attempted to reinstall tf2, remove config / custom folder, close geforce experience, update drivers, and restarting
cpu : amd ryzen 3600
gpu : geforce gtx 960
ram : 16gb
motherboard : asus prime x570-p
main monitor : acer GN246HL 144hz
2nd monitor : asus VE248H 60hz
if u have anything i should try, please let me know