Kong Soo Do is a not a formalized system of martial arts, and the styles used by the various kwans are influenced by the individual backgrounds of the respective founders/head instructors.
Yun Mu Kwan was founded by Chun Sang Sup (전상섭) learned Okinawan Karate from Gichin Funakoshi.
After Chun disappeared in the Korean War, his original students voted for Master Yoon, who trained in Chuan Fa in Manchuria, as the Jidokwan's first President.
The Kwon Bop Bu/Chang Moo Kwan was founded in 1947 by Yoon Byung-In who had studied Chinese Chuan Fa under the guidance of a Mongolian instructor in Manchuria.
In addition to Lee Nam Suk's work with Chang Moo Kwan, other of Yoon's top students also carried on his teachings, namely; Park Chul-hee, and Hong Jong-Pyo (both Kang Duk Won).