How might Dupin be a double for Poe himself?

On the surface, the detective C. Auguste Dupin seems very different from Edgar Allan Poe. Dupin is French and lives in Paris; Poe was American and lived in Richmond and Baltimore. A side-by-side list of differences would be quite long.
Yet Poe clearly pulled some of Dupin's characteristics from his own personality and habits. Like Poe, Dupin is poor and must earn a living, and his fortunes had declined. The brain power and meticulous attention to detail are also things they share, along with an unusually high level of education for the day. Poe endowed Dupin with the mental ability he employed and admired, "ratiocination," creatively applying intellect and psychology to understand another person's reasons and actions.
Dupin is also a poet.
And let us not forget, Poe had the cunning brain of a detective because he was the one who thought up the mysteries and codes that he sets Dupin to solving and deciphering.
While Dupin is not entirely unique in the French social world Poe portrays- there are policemen solving crimes- as a type in literature he was quite new: the first private detective hero. And even though Dupin's France may owe more to Poe's imagination than to historical reality, the French readers and literati were quicker to appreciate Poe's genius than were his fellow Americans.
https://www.britannica.com/biography/Edgar-Allan-Poe

Dupin admits to the prefect that he is "guilty of certain doggerel myself" when the subject of poetry arises. Poe was a prolific poet.
Dupin is a highly educated, scholarly, and intelligent man with deep knowledge of mathematics, philosophy, deduction, physics, and language. Poe had a very good early education at Stoke Newington outside London and briefly studied at the University of Virginia and West Point. Though troubled, Poe was clearly highly intelligent and a creative thinker, like Dupin. Dupin surrounds himself with books and musical instruments, items that were certainly a major interest of Poe's.
Dupin is a man who had been born into wealth and position but has been reduced to genteel poverty. For a relatively brief period in Poe's life, he was taken in by John and Frances Allan, a wealthy Richmond couple who fostered him, took him to England, and arranged for his education. After Frances's death, John Allan disavowed Poe, who then fell into poverty.