Yes but depending what the second is displaying may not be much. Say if the second only shows a browser tab and not a game your playing.
So i have a gtx 1050 ti, and i was thinking of buying a new monitor that can display 1080p, since the one that i have right now only displays 768p and down. And then i thought of using both of them at the same time. The 1080p for games, and the other one for normal stuff.
That wouldn't impact your performance much at all, as long as the application you have open in the second monitor isn't very demanding. For example, I used to run ARK on one screen, and Chrome on my other, and the second screen didn't cause a noticeable difference in performance.
However when I got a bunch of tabs open, or watched a youtube video or some more demanding application, it would impact the performance of the game I had up on the other monitor.