if do you get a 144mhz you better make sure is 1080p, you wont get high enough fps with 1440p, the monitor needs to be g-sync as well since you have nvidia card
Personal preference & how much you are willing to spend are what matters.
The 1060 can do high-frame-rate-gaming @1080p easily. Or, you could do 4K @30fps (Med-High settings) or you could do 1440p @60fps (high-V.high settings).
1080p High Refresh TN panels will probably be the most affordable, but don't expect Gsync without shelling out some extra cash. I can elaborate on any of this for you but what you "should" buy is up to you.
144hz always makes for a better experience. Especially if your gpu isn't top shelf like my 480. I'm getting one next month with FreeSync as well for $179