"Sam Gor" is probably a myth or - as is the case with "Brother's Circle" - just a designation to describe a cooperation between a group of criminals.

And seeing a lot of articles seem to describe them that way; Big Circle Gang isn't a Triad. Triad groups are mostly Hong Kong- and Taiwan-based and are largely connected to a certain community.
For instance, 14K has traditionally been the Cantonese group and has a lot of links with Guangdong. Sun Yee On on the other hand is connected to the Teochew community. The Wo Group has different branches; Wo Hop To is traditionally Cantonese, but the biggest out of the Wo branch, Wo Shing Wo, was formed in Sham Shui Po which is a Hakka stronghold. Nowadays their powerbase is more in Tsuen Wan (which is also an area with a strong Hakka contingent, even though most Hakka in Hong Kong are speaking Cantonese these days).
The Bamboo Union in Taiwan on the other hand is connected to the Mandarin-speakers (from Sichuan, Yunnan, Zheijan, Anhui, Jiangsu, Jiangxi) who came to Taiwan.

Big Circle Gang on the other hand was more formed as an organized street gang consisting of Cantonese/Taishanese speakers from the Guangdong province. Largely Guangdong (especially from Guangzhou and the outskirts) based criminals that aren't directly connected/employed by a Triad organization (loosely) band together to conduct criminal operations.