Ghost594 :
Hey! I have a 144hz and a 60hz setup too and they work just fine (both have displayports, like psycrow mentioned it's better). The only limitation you're gonna have is that the 60 hz one will cap the 144 hz one to 60 hz if you're running anything involving fullscreen graphics on the 60 hz one. I realized this while trying to play hearthstone on the 60 hz one while doing smthn else or playin some other game on the main 144 hz one. Did my research, apparently it's not a bug, it's just what the card can handle at the moment, even tho older cards didn't have this problem which is a pity. So if you don't intend on doing that, you'll be just fine! If you got any more questions, i'm glad to help!
I'm in a similar situation Here's my dilemma.
last week, I just built a personal gaming pc. I had no trouble running 1 monitor. I then decided to start streaming again to twitch, so i hooked up my Asus VS247H (60hz) to be my second monitor, to read chat/prieview stream in OBS, etc. I am using the Asus VG248 (144hz) monitor to actually game on. The problem that im encountering is that whenever I have a website open such as twitch or youtube and a video is playing, my in game FPS on my first monitor drops from 144 to 60 immediately and stays there. Even something as small the chat bubbles in skype flickering when someone talks, interrupts my FPS on the main monitor. The second I MINIMIZE the application or website, the FPS returns to 144hz. Is there a solution to this? Also the 144hz monitor is connected using a display port cable, the 60hz monitor is hooked up via HDMI. (both are plugged into the GPU.)
Edit: currently running the 382.05 driver (i uninstalled the 383.33 since that failed me as well.)
SPECS: Geforce GTX 1080ti, i7-7700k, 16gb RAM, 250gb SSD, 2TB HDD, MSI z270 krait gaming motherboard, evga 1000w power supply, Windows 10 Pro