People have said both Japanese and Traditional Chinese are faster, but which one is actually faster?

Japanese

Less characters, which means less text.

I dont know the difference between the languages, which one is japanese?

See this:

https://www.speedrun.com/smo/thread/a99zi/1

@IwerSonsch Japanese is slower than Chinese.

The fastest language is Traditional Chinese which is the 2nd option from the bottom in the language menu.