Usually people run in borderless windowed (allows to alt-tab around desktops to do other stuff while playing a game) or in fullscreen.
The way most window managers work, typically when running in borderless windows, your window manager is actively rendering your desktops so that they are primed and ready to be tabbed over to. This uses up some of your graphical rendering power.
In fullscreen all your graphical power is used to render the game. This is why the screen goes black and takes a second to display your desktop if you switch to your desktop from a fullscreen game.
Bordered window should be the same or worse as borderless window, with how the window manager is optimized for your particular graphics package being the deciding factor on how much worse it is than borderless window.
Similar a super well optimized window manager won't have much of an impact between fullscreen and borderless window.
Also depending how your window manager is organized, stuff like having multiple desktops or lots of windows/tabs may have more of an effect.