Where/how are default input methods stored?

I use the Cangjie input method to type Chinese characters. The one bundled with macOS is an older "version" of the input method that I don't particularly enjoy using. So far I've been getting by with using a third-party IME (Rime) but for various reasons it's not ideal either. I know that Macs support custom plaintext *.cin files but I'm looking for something different.

I'm curious where and how default Chinese and Japanese input methods are stored in general. Maybe a filepath, and if the file is in some esoteric format possibly external software to read/edit the data? My goal is to see if I can write a script to change the character mappings to the ones I'm accustomed to.

Hope this question isn't too specific. If this is better suited for another StackExchange forum just give me a heads up and I can ask it somewhere else.

The Chinese and Japanese IM's (along with several others) are in System/Library/Input Methods.

For some alternatives that may offer more options, see this page.

https://m10lmac.blogspot.com/2017/05/macos-alternative-input-methods-for.html