> I believe that React and similar frameworks run a diffing procedure to find out which parts of the UI actually need to be updated (so a more minimal set of updates is actually applied)

That's true. React diffs the virtual DOM and applies the changes to the actual DOM. However, the fastest is still to diff the actual data to be rendered, and determine whether the render function needs to run at all (this is opt-in via React's shouldComponentUpdate() lifecycle method).