Serg, hello,
the aim of this mod is to bring in new elements to the game. The main focus is on hero development. I always say to you will need at least 3 full games to understand the idea of the new content. Once you understand how it works, it can offer a nice new reward system with new experiences.

Increasing the power of spells is probably much easier than you think. At around 30-40 Magic Strength your spells will be at the same level as in original H3. This should be easily achievable by any wizard class. With Spell Trainer mod it will go even faster.
The Nobility skill is actually easy to understand. Walk-in your castle and click anywhere, a screen will show you how many more creatures you can hire this week. This can be done once a week for every hero that knows Nobility.

Edit:
By the way, Berserker implemented an option to turn of the class system At the map start, just activate "Berserker Option"+"Choose Class". Once the window opens up and asks you which class you want to become, you say "Never Ask Again". This will allow you to learn Master+Grandmaster skills without restrictions.

Edit: The Kingdom Overview currently cannot be returned, it crashes the game . I am also not happy about this, but the truth is that the income of resources has never been accurate in the Kingdom Overview because of the the many modifications that are not taken into account by the game.