I’ve just installed Fedora 23 on my gaming computer at home, switching from Mint 17.3.
I have an nVidia card (using RPM Fusion to install the non-free drivers still necessary to get any kind of 3D performance out of it), and an Eizo Foris monitor capable of running at 120 Hz refresh rate. It took me a while to figure out how to make the latter work in Mint (create a ~/.config/monitors.xml). Unfortunately, this approach – along with a number of others – didn’t work in Fedora 23.
The solution (and its cause) was embarrassingly simple: I followed the general gist of the initial posts in this discussion thread, using xrandr to output the necessary data and creating a Gnome autostart item (~/.config/autostart/xrandr.desktop) which starts xrandr with the correct output, mode and refresh rate options. I did not disable the Wayland session where gdm initially runs.