With a 970 and a crappy tear happy monitor do you think I should use fast sync rather than adaptive vsync? (Even with adaptive it tears)
Since I bought my 1700 I've had to cap the frames in BF1 to 60 fps as system too fast now for monitor.
Only one way to find out really - test it and see.
One thing worth testing with FastSync as well is the effects of things like framerate caps (generally you don't want them) and max pre-rendered frames - not sure if the nVidia drivers over-ride it in FastSync mode or not but some games have their own setting - increasing it slightly can potentially actually have positive effects with FastSync especially if you are using low values for minimum latency.