Hi MirceaKitsune,
Welcome to the Ogre world.
Yes, the OverhangTerrainSceneManager looks great.
Unfortunately the development stopped at the level of a "technical demonstration".
The code shows how height map can be modified like a mesh, but it's not optimised.
So edited terrain will cause lower frame rates. (Maybe because of a missing LOD management?? I'm not shure.)
If I remember right, the creator stopped his development, but (unfortunately) nobody continued it.
Technical:
The OverhangTSM is an extended version of the Terrain Scene Manager.
It's an old terrain solution of Ogre. It was fine, but not it's replaced by the Ogre Terrain Component. The Terrain Scene Manager was removed in Ogre 1.8.
Theoretically the OverhangTSM can work in Ogre 1.8, too.
But as you see, the code needs some updates.
I'm not shure - maybe someone applied some updates (to Ogre 1.7?). Search for it in the latest posts of this topic. Some months ago somebody created a public repository for that.
If you manage to make further updates (solve compiler problems), it would be nice if you publish the updated code. The best would be to ask the repository creator for write access. This is better than a download link or an additionally repository.
For a game like Mindcraft the Ogre class
ManualObject is very nice.
By this it's easy to create custom objects by code. (Additionally it can be converted to a mesh and saved as mesh file if needed)