I recently switched from a GTX680 to an R9 280X so I could run F1 2017 (MacOS, Steam) more reliably. I had hours of fun with F1 2016 using the GTX680 but at least on Sierra with the Nvidia card and the web drivers it wasn't 100% reliable running F1 2017. It did run and I could do some time trial laps etc. but I often lost audio (strange for a GPU issue) between the menus and in car, plus I had some crashes where the video stopped and I had to force quit. These all went away with the AMD card. I'm on High Sierra now and the R9 280X is still running it well so far (I'm using 1440p and medium, now on round 8 of my 100% distance career). Maybe however the new web drivers and High Sierra are better but I'll be selling it and if I do change GPU again it will likely be to an RX580 because of the likely support thanks to the iMac.