I recommend using "Borderless Gaming". It's a program that makes games running in a Window become borderless. It even fills up the screen for you, so you won't have to do some manual resizing. Just remember to make sure the game isn't running in Fullscreen, though.
P.S. If the taskbar is still there after the program does it's thing, click on the Taskbar and then click back into the game. Should get rid of it.