Triple BufferingGraphics tab of the game's options.VSync in the Path of Exile game client.Foreground FPS settingSet your Processor Power Management to never reduce your CPU's state below 100%.
Background FPS settingTools such as AMD Radeon Chill, NVIDIA Control Panel, and RivaTuner can potentially impose FPS caps.
For testing purposes, try disabling G-Sync or FreeSync.
If your high refresh rate monitor has been capped to 60 Hz, your FPS may seem lower than you are used to.