Huang Tingjian, Qin Guan, Chao Buzhi, Zhang Lei
Huang Tingjian's poetry is a school of its own, and he is as famous as Su Shi, Mi Fei and Cai Xiang in calligraphy. He was called "Song Sijia", and his writing was slender, which even influenced Song Huizong Evonne, the founder of "Thin Gold Body". Therefore, among the four bachelors, Huang has the highest achievement.
Qin Guan's ci style is rich and graceful, probably because his talent is not as good as Su Xiaomei's, which makes him one of the four bachelors with the most folktales.
I don't know much about the latter two. Probably Chao came from an official family and was deeply influenced by Su Shi. Influenced by Bai Juyi's Zhang Ji, Zhang Lei's poems are simple and straightforward, with graceful words. Representative works include Romantic Son and Journey of Youth. You can have a look.
They are all called "Four Bachelor of Su Men" by later generations because of Su Shi's guidance, but they have different styles and accomplishments.