I installed nvidia drivers 378.10.10.10.25.102 and so far it seems to work better
That's not going to help, trust me. This is definitely an Apple issue because I had 0 issues with Sierra and WebDrivers on a Mac Pro 5,1.
There's some type of memory leak in WindowServer.
A fresh boot works fine for a bit but once you start using Photoshop, Lightroom, Chrome, the GPU VRAM fills up and it starts to lag.
Try it for yourself. Instal iStat Menu and look at what happens with the GPU RAM.