My personal +1 on a much lower system (RX 580 and with the disclaimer that I always use Graphics 3 and I always had the Special Settings mentioned just before)
It had a VERY hard time loading it (loading bar phase, I logged off at Serbule in the city) to the point it lagged my entire PC and it did so again while re-entering from Hills, to the point it pushed me to a Reconnection and back to Hills twice before I could actually enter (such things didn't happen before)
Interestingly enough though while at Serbule, the FPS seemed the same low-ish (around 30~40) while inside the city BUT when leaving it, specially going down (to hills/after stalls) it had a massive stutter and FPS drop, a huge dip that got better and almost went back to 60 after a while but still unstable and with the mentioned "hitches" it's literally some hiccups, every now and then...
Looks amazing though! Love the new textures and stuff like the bridges and I was able to see some of it at night, it's very nice