Dual Monitor: Games Lose Smoothness If I open Firefox or Whatever in the 2dary Screen

[Warste]

Hello!
ill describe my rig first..

I7 6700K 4.5GHZ
16GB DDR4 3200MHZ Avexir Blitz Red Led
MSI 1070 GAMING X OC 2100MHZ

Not sure if anyone already asked but im having what i consider a weird issue..

I have 2 monitors, a AOC G2460QPU 144HZ 1MS 1080p and a Samsung SA300 60hz 768p, i usually use the 2dary monitor por browsing, checking HWMONITOR, Discord and OBS Studio

Main monitor its plugged with DisplayPort
Secondary monitor its plugged with HDMI-DVI cable

The thing is, i notice that i lose smoothness while gaming even if i dont lose ANY fps.. games like LEAGUE OF LEGENDS! which its a joke for my rig, i have it capped at 144fps, and if i open a guide in my 2dary monitor, i feel it like im at 30fps... but FRAPS and the ingame fps OSD show 144fps...
i tried PUBG with rivatuner OSD to check the frametimes, and with the game alone vs the game with OBS in the 2dary monitor, i have the same fps, the same frametimes, but it feels like 30fps :S

Any ideas? any aditional info i could put in here ? i would understand some performance impact if i had youtube for example, but not this :S

Thanks!

 

[Kkkk1]

I don't understand what you mean by lose smoothness even your FPS doesn't change?? Can you elaborate a bit more please?
Thanks.