Dr. Stephen Albert, a man of philosophy, is surrounded by the objects of a scholar: a library of books, a writing cabinet, fragments of a letter. The Chinese lantern he carries is a sign of the cross-cultural loyalty that he has developed through years of study. The phoenix figure in his office symbolizes eternal rebirth, a clue to the thematic nature of his work as well as a suggestive nod to his reenactment of Ts'ui Pen's life.
Yu Tsun, on the other hand, is a man of action, not scholarship. We associate him with practical items: a watch, keys, some change, and a gun with a single bullet. We know from the moment he empties his pockets that he's going to make something happen.
Yu Tsun and Captain Richard Madden are spies, a job that by definition involves betrayal. Yu Tsun betrays Stephen Albert, and he also betrays himself. But that's why he's a spy – the world of espionage is not characterized by a great deal of trust.
Dr. Stephen Albert, on the other hand, is a scholar. Like Ts'ui Pen, he devotes himself to endless study of abstract concepts, philosophical texts, and the translation of languages. His role as a scholar explains both his great wisdom and his solitary lifestyle.
Dr. Albert, like Ts'ui Pen, secludes himself in a pavilion at the center of a garden. His pavilion is a scholarly retreat that allows Dr. Albert to contemplate nature and focus on his studies. This center of seclusion and wisdom has its counterpart in The Chief's office, another stable locale from which he exercises great worldly power.
Yu Tsun and Captain Madden, on the other hand, are agents on the move. They pass through boarding houses and train stations in pursuit of more powerful men's interests.
Characters' nationalities in this story go a long way toward explaining their motivations. It's important to recognize that this is due to the historical context of the story, not because Borges is necessarily asserting that there's anything essentially characteristic about being German, English, or Chinese.
The fact that Captain Richard Madden is Irish, for example, explains why he is, as Yu Tsun puts it, "obliged to be implacable." An Irishman in the years of the movement for Irish independence would have to go the extra mile to prove his loyalty to his British bosses. Likewise, Yu Tsun's Chinese origins represent both a conflict for him and a source of motivation. The emotional struggle between the balance and honorability of his former life in China and the pragmatics of his life as a spy in Europe causes him great anxiety. On the other hand, he does what he has to do because he wants to prove his value to Westerners, despite his foreignness.
The fact that The Chief is German establishes him as a villain – a citizen of the "barbarous" nation that, in this WWI context, has degraded the protagonist by making him a spy. On the other hand, Yu Tsun holds up Goethe, a German writer, as a paragon of cultivated civility. Clearly Borges wants to make the point that national reputations can change – and so can individuals. For example, Dr. Stephen Albert, a "barbarous Englishman," adopts many of the customs of the culture that he studies, acquiring through habit and devoted scholarship a sort of transcendent cultural identity.