I'm a bit confused on the classification of striking CMA. Do practitioners divide it into these general categories (understanding there may be several or dozens of variants of each)?
kung fu northern
kung fu southern
taiji
bagua
xing yi
other?
How do you see it?
Taiji, Bagua, and Xingyi are all Northern Chinese martial arts.
What is Northern vs Southern is defined by whether the art originated north or south of the Yangtze River (the longest river in China).
Generally speaking, martial arts from similar regions tend to have a lot of overlap in martial art usage.
For example, if I look at skilled old-timers show applications in Bajiquan, Northern Praying Mantis, or Baguazhang, I can go: "Oh! That looks like our application in this sequence."
And that's because they're all Northern Chinese martial arts; they will be overlap.
But conversely... this means that if a martial art style has none of those applications that everybody else in the surrounding region has, that makes them the outlier. That could be a sign of a broken transmission.
Another classification for Chinese martial art usages is: Ti (Kick), Da (Hit), Shuai (Throw), Na (Seizing, joint locking/Qinna).
The ratio of each of these four varies from style to style. Some styles may be underdeveloped in one of these four areas.