When it is not going to view in detail and the geometry of vertices isn't important.
As you said, there is no extra vertices created, which mean, if there isn't a geometry, rendering engine can't render on that pixel. Commonly seen in early game when we can't afford high vertices computing.
As a same result, AO, shadow, light bounces cannot be ...
For example, you cant 3D print a normal map as well as you cant set some physical actions to a normal map. In short. If the surface is just for looking and for not so important parts or if there is just no noticeable difference, use normal map. It can shows some geometry or shadows and light bounces not so realistically.
If you expect to use the surface for ...
Steps for creating the below image:
take the default cube
add a subdivision surface modifier set to simple, with 7 levels
add a displacement modifier and choose your image texture, adjust strength so it doesnt displace it too much.
The actual engraving gets done with the displace, where you select Image Texture, and then use whatever image you want. ...