guys, i'm currently talking to BenQ about the situation but to avoid any confusion here, this is the issue as it stands:
If you connect the XL2730Z to a FreeSync system then the AMA function (overdrive circuit) is disabled. It doesnt matter whether you have FreeSync ticked or not in the graphics card settings, it is still turned off. If you "break" the end to end freeSync system by doing something like switching to DVI instead of DisplayPort, or using a non-FreeSync supporting drive, AMA behaves as it should. obviously if you use the screen from an NVIDIA /Intel card or a non-FreeSync card then it behaves as it should.
AMA High is much faster than AMA off, as with it off there is a lot more blurring (hence the reported blurring problems of FreeSync). So at the moment connecting the screen to a FreeSync system is not great, as although you get the benefits of dynamic refresh rate, you have much worse response times and more possible blurring.
This is apparently an issue affecting all FreeSync screens and will require both an AMD driver fix (being worked on i'm told) and a firmware update for the FreeSync screen. i'm pending info from benQ about what is needed for the XL2730Z and how that will work.