This means your system can't keep the emulator running at fullspeed so vsync cuts your framerate in half since it doesn't have tripplebuffer to feed a pre-drawn frame while drawing the new one. When you use borderless fullscreen, you're by-passing vsync and letting the Windows Desktop Manager keep the game's video output in sync with your monitor's refresh rate without halving the framerate, but just repeating old frames. This avoids screen tear but causes minor stuttering that can be worse on some games than others, but is a reasonable compromise.
My description of how this works may not be perfectly accurate but the bottom line is that borderless fullscreen is a decent compromise to vsync when you can't maintain full speed but want to avoid screen tear without drastically reducing your framerate. For games on which you are able to maintain full speed, vsync will give you a smoother video output with no stuttering.
My description of how this works may not be perfectly accurate but the bottom line is that borderless fullscreen is a decent compromise to vsync when you can't maintain full speed but want to avoid screen tear without drastically reducing your framerate. For games on which you are able to maintain full speed, vsync will give you a smoother video output with no stuttering.
Windows 10 Pro x64 | i7-9700K @ 4.6-5.0GHz | MSI Z370 Gaming Plus | MSI RX 5700 8GB Factory-OC | 16 GB DDR4-3000