“I know that with this two workers I can make my whole game with enemies, animals, movement, etc…”
You can. What part of the documentation made you think otherwise?
Think of the client worker as your player computer and the UnityGameLogic worker as a server, keep in mind that this are very broad generalizations though, but they’ll serve for now.
So the UnityGameLogic is responsible for all the processing server-side, things like player movement validation and synchronization, hit detection, health validation and updates, power up enabling/disabling, spawning/respawning, etc…
If the scale of your game is too big, you may hit a processing bottleneck on your UnityGameLogic. This is when you split your login between two or move UnityGameLogic workers. However, when you first start developing your game one single UnityGameLogic worker should be more than enough.