What is the most reliable (accurate) method of determining the frame rate a composition is running at? Related, is the Vuo window always locked to screen refresh or is there a way to create a window without vsync (old terminology, don't know what the right term is now).
Most reliable is to look at the port popover for the trigger driving the rendering.
For a rate other than the refresh rate, you can use
Fire Periodically. (The reason that the window nodes always fire at the refresh rate is to avoid screen tearing.)