Hovering over the green 'expand' button on any document window (but not secondary/stand-alone windows), shows the full screen toggle. click when this is showing to enter the normal macOS full screen mode. It is not possible to use this for tear-off pop-up windows (e.g. Get Info, etc.) or for note text windows.
Full screen split view is supported. In normal (non-full) screen mode press and hold the green "full screen" button in the main window's upper left-hand corner; the window will shrink to permit the user to select the right or the left half of the screen.