It's various minor things. Like PADDs being proper LCARS tablets with a bit more space for content, smaller bevel[0] and even portrait mode[1]. Or the experiments with circular (radial) elements on display, which arguably are now decorative, but still they fit in, so are a good starting point for further exploration.
Or, and I can't find a screenshot of it now, that one tiny joke that made me almost spit out my tea. A scene on the bridge, the captain talking to someone over the viewscreen; she makes a gesture to cut off audio, the tactical officer presses a button on his console, and a small icon of a crossed out speaker appears on said console. Immediately recognizable even for non-StarTrek audience, and still they made it fit the style.
