Hey Brian,
Made a separate thread for your questions re: Vietnamese WCK. I’ve gone over some of this before, but it will be good to put it all in one place.
Yuen Chai-Wan learned alongside his younger brother, Yuen Kay-San, under Fok Bo-Chuen and later Fung Siu-Ching. He didn’t teach much (he preferred fighting) but what he did teach in China is similar to what Yuen Kay-San taught. Later, he moved to Vietnam and taught first in the north, then in the south. His ethnic Cantonese students (Cantonese people living in Vietnam, or of Cantonese descent) seem to have learned very similar to his Foshan students and what Yuen Kay-San taught, including 3 forms, etc. His ethnic Vietnamese students seem to have learned less, mostly Siu Lien Tao.
Also, keep in mind that while everyone and his sibak traces back to Yuen (Ngyuen Te Cong as the pronounce it) others were also teaching in Vietnam at the time (such as Lui Yiu-Chai) so different influences exist.
Those of Vietnamese descent, survival more important than lineage during very turbulant times, picked up and added additional material, especially 5-animals related material and extra weapons such as tiger fork, straight sword, etc.
For cultural reasons, like the Chinese, they’ll attribute everything back to a famous founder, if different say its a secret/better version, and if they can, link to Shaolin, mysterious monks, etc.
There are now many distinct lineages in Vietnam, and a lot of politics (the typical “I’m the true successor” (in their case, they use the term “patriarch”) and “we’re the original branch”) and strange histories popping up (unfortunately, perhaps derived from Complete Wing Chun and/or the Archives as they changed shortly after that time).
Some discrepencies might also be based on fragments of information (for example, Nam Ahn includes Yuen Kay-San’s children as senior students under secret monks, etc. and they did not practice martial arts and were quite a bit younger
)
“Diamond Temple” is another example of this. Diamond is just a symbol of Buddhism, eg. Diamond Palm is Buddhist Palm.
Anyway, its quite an involved topic, but this should get it started.