I have a slightly different issue but seems possibly the same. My gaming laptop kinda broke a couple days ago. The internal battery had bloated and caused my laptop screen to crack. So I sent it in to get just the screen replaced as I had already removed the battery and figured that I usually have my laptop plugged in mostly so I did not need it.
However, prior to the laptop screen fix, my game was able to run smoothly on a mix of High/Ultra settings. However, once I had issues with the battery, it did cause the game to run almost like the entire laptop was in power saving mode. I've since had the laptop screen fixed and on testing a couple of other games (Assassin's Creed Black Flag and Football Manager), it seems to be working fine. However, when running 7DtD, its like its stuck running on power saving mode. The game's FPS took a nosedive from 70-80 FPS usually to pretty much single digits with lots of screen tearing. So far, I've tried reinstalling the graphics driver and all but doesn't seem to have fixed it. Have tried reinstalling the game but it doesn't seem to have fixed it... anyone able to give any advice?