A couple of questions regarding a small game change. Auto-translated

Hello, I hope there’s someone knowledgeable who can answer my question or at least point me to where it’s already described in detail. I’ve been searching, but I haven’t found a detailed description for beginners. I’ve been playing Heroes 3 for over 10 years, and now I’ve finally decided to change something in the game to make it more enjoyable:
- How can I change the production of one unit to another in a town? For example, instead of centaurs, elves should produce hobbits.
And I want this change to be reflected in any map, no matter which scenario I launch.

I would gladly say something specific, but I will only say that there is a mod somewhere on the internet that prevents creatures from being in castles. Yandex knows everything. ;)