How does countering world items with other items exactly work?

In anticipation of the new volume, I decided to re-read the entire series, and in volume 3, I started wondering: Ainz mentioned that the only way to defend against a world item is another world item. It was also mentioned that he gave the World Items to Aura and Mare to protect them from other World Items. Question - how then can the world item "World Savior" destroy the entire Nazarick (According to Momonga) if its effects on some players would be offset by 10+ world items that they had? Does this mean that because of his World Item, Ainz is immune to all World Items? To the spear of Longinus too? Or strongest twenty items are immune to protection of the other world items?