Deadpool became Deadpool through a series of complex and sometimes convoluted events in the comics. He was originally a mercenary named Wade Wilson, who underwent experimental treatments that gave him his unique powers and personality.
There were a few novels that fit this description, such as Legend of the Earth Emperor, Mountain God in the City, Incense Becomes God, I Actually Became a Mountain God, and so on. You can choose one according to the plot introduction of these novels and your own taste. I wish you a happy reading!
There is a loose link. The version of Deadpool in Wolverine Origins provided a starting point, but the standalone Deadpool movies developed his character and story in a more distinct and expanded way, deviating from the initial portrayal to create a more focused and engaging narrative.
It's a bit of a mixed bag. While there's a link, the portrayal of Deadpool in Wolverine Origins doesn't fully align with his later, more developed storyline. Some elements were changed or not fully explored.
Jiang Ziya was a historical figure as well as a mythical figure. In ancient Chinese mythology, Jiang Ziya was a famous politician, military strategist, and counselor, and was honored as "Jiang Taigong". Legend has it that he was originally a feudal lord at the end of the Shang Dynasty. Later, due to some reasons, he abdicated and became a civilian. When he met an immortal while fishing, he received the guidance and help of the immortal and became an outstanding politician and strategist. In ancient Chinese novels, the image of Jiang Ziya was often depicted as a god or hero with superior wisdom, superb strategy, and martial arts. He was used as a symbol to inspire people's wisdom.
Obviously, the main characters are the two Deadpools. They are both versions of the same character but with potentially different backstories and personalities in this graphic novel.