To answer the OP's question about matching FPS and refresh rates in a nutshell; monitors can't refresh part way through a cycle. If you have a 60Hz screen then it can only refresh on the dot of each 1/60th of a second.
If you have a graphics card putting out 40 fps, then that doesn't slot into the 1/60th timing of the monitor. Sometimes there won't be a new frame ready, so for 2/60ths of a second, you get the same image. Then there is a new frame - but that's already been in the buffer for a while, and this frame only gets displayed for 1/60th because the GPU was already part way through the next frame while this one was waiting to be put on screen.
The result is that you get a 2-1-2-1-2-1 pattern, which is effectively bouncing from 30 to 60 fps and feels worse than a steady 40.
That said, 144 is a good number because a) it is high, and b) it divides by a lot. If it does get forced into a 2-1-2-1 pattern by, say a GPU giving you 100, then the lower band is 72fps, which is much more tolerable. You can also look at framerate capping to 72, or even 48, which should be very sustainable with your system
(Disclaimer; post above is 'the best of my knowledge'. I don't mind being corrected if inaccurate!
)
If you have a graphics card putting out 40 fps, then that doesn't slot into the 1/60th timing of the monitor. Sometimes there won't be a new frame ready, so for 2/60ths of a second, you get the same image. Then there is a new frame - but that's already been in the buffer for a while, and this frame only gets displayed for 1/60th because the GPU was already part way through the next frame while this one was waiting to be put on screen.
The result is that you get a 2-1-2-1-2-1 pattern, which is effectively bouncing from 30 to 60 fps and feels worse than a steady 40.
That said, 144 is a good number because a) it is high, and b) it divides by a lot. If it does get forced into a 2-1-2-1 pattern by, say a GPU giving you 100, then the lower band is 72fps, which is much more tolerable. You can also look at framerate capping to 72, or even 48, which should be very sustainable with your system

(Disclaimer; post above is 'the best of my knowledge'. I don't mind being corrected if inaccurate!
