Just a quick question… does the network engine make any extrapolation or must I do it myself? The docs mention it but it’s not clear to me if they do it because it’s a built-in feature inside the engine or just to tutorialize the users 
Its not automatic. How you do it depends on what you are doing, i.e. what you are extrapolating. For example, in an FPS the movement of players might be really erratic so extrapolation will only be usable for very short delays (or not at all really), but for a car game or flight simulator, you might do it with a high degree of accuracy for longer delays in traffic.