if you are looking for picture quality you have to go with an IPS panel, but they are 4-5ms. Honestly I don't think people can tell the difference between 1 - 4ms. anything below 5 you are good to go.
at 27" the sweespot is 1440p.
I can recommend what I own because I went through the same research and thinking a couple of weeks ago. I chose the PG279Q which is IMO the best out there with those specs. and you definitely have the budget for it since you went with a GTX1080.