I would consider the NB-MED guidance document to be the most useful and most powerful. This is based on the governing power that writes said document. The NB-MED guidance documents are written by the Notified Bodies, which have more central power than the Competent Authorities as they are the central piece of the EU regulatory. They are also the ones that wield the power to approve or fail a device, so it would be in the best interest of manufacturers of devices to follow this for guidance. They are also the body that audits these manufacturers.