Where different block designs are available there is a gear icon at the recipe to choose which one you want.
For the other questions:
- Shale Bricks are not necessarily harder. It depends on where you live for the availability of the resource. In multiplayer people are spread out and hence we offer different recipes. They do not need to be of the same 'difficulty', sometimes it's just more convenient based on where you are.
- Windmills and Water Wheels will likely get an extension when they actually require wind and water which they currently do not.
- I've not heard of that linking bug yet, you might want to report that on GitHub.
- The Kiln is indoors for balance reasons.
- Metal being harder to find is intended, it's still very easy once you got the hang where to find it.
- I agree on pottery, but for the current progression line it best fit there, stuff will change with more content coming.