visit the modding section
https://forums.taleworlds.com/index.php/board,416.0.html
Tweaks thread has a list of know changes you can use. You should check there and maybe add your query too.
You can download the game source code and modify it yourself (easier than .txt tweaks)
You can use the [VC Tweaks Tool]
Q&A for modding thread helps with links, tutorials, etc