Window types generally have nothing to do with which window buttons should be visible. Window type dictates if there is a titlebar, and if so then...
Close button: Must always be visible because apps exist which have no other way of closing their windows.
Maximize button: Should only be visible for a window whose resize constraints allow it to be maximized.
Minimize button: Almost always visible, unless the window is modal to its parent.
Window types generally have nothing to do with which window buttons should be visible. Window type dictates if there is a titlebar, and if so then...
Close button: Must always be visible because apps exist which have no other way of closing their windows.
Maximize button: Should only be visible for a window whose resize constraints allow it to be maximized.
Minimize button: Almost always visible, unless the window is modal to its parent.