First, I want to say Freesync is working in NieR Automata! I tried it with and without fullscreen mode, it is day and night. In fullscreen mode, Freesync is activated and the smoothness is absolutely noticeable. If I turn off Freesync, I can see stuttering in fullscreen.
My issue is that tearing is heavily loaded in 1920x1080 resolution with Freesync on. It should not be the case since Freesync is supposed to remove tearing in the Freesync range. For now, I have to turn on VSync but it adds noticeable input lag. It's of course still playable but it would be much better without VSync.
I tried VSR in 1440p and it reduces drastically the tearing but some remains and pops occasionnally.
My system is
Windows 10 64bit last update
R9 290 tri-x
Samsung 27" C27F390
Freesync range is 40-72
My average fps is 55.
NieR:Automata in fullscreen mode, 1440p (vsr), vsync on.