Minecraft General

Is this the optimal way? The blocks should be used as a normal/basic building block, so there may be hundreds or maybe even a thousands of them in a single chunk.

For sure it is possible to do this, and in fact it has already been done. However it is not really a simple thing to achieve, specially if you are new to modding..you may want to take a look at the MIneColonies mod, which implements npcs that literally do what you want, and start exploring the vanilla code that handles villager entities

Hello,    is it possible to do this? I'm new to modding and I would like to for example create a npc, that collects some wood and build a house.

You need to add a TileEntity to your block to store arbitrary data.

A link to what?