i use a asus mg 279 with my gtx 1080. just leave freesync off, as it wont work with the card anyways. its a 144hz panel anyways so i can just use vsync if i really want to.
I have the Asus 248q freesync monitor with a gtx 960. Don't have a single complaint. Freesync and gsync is just a gimmick. I haven't noticed any stuttering.
FreeSync is AMDs alternative to GSync. They are not compatible. Having a Nvidia card with a FreeSync monitor (or AMD card with GSync) is the same as having that card with Vsync.
It will work like a regular monitor, because nvidia blocked freesync in their drivers(bs move, as freesync is open sourced, even Intel said theyre going to hop on it.)
I use an LG 22MP68VQ, 1080p, ips LED monitor with 75hz refresh rate and amd freesync with a 750ti. It works flawlessly and 75hz definitely feels a lot smoother than 60.