Hey! Thanks for trying out The RPG Engine and for the very kind words. It's great to hear it's heading in the right direction.
At the moment sharp edges can be created by using a smaller brush around curved top of the slope, this will push the edges out and create more of the effect you are looking for. In future I will absolutely be looking at how to optimise the building process, both in the terrain sculpting as well as the Prop placement (and colouring). There are some things I will be adding first such as a major Ui update, custom item importer and player sheets. After these core elements are in, tools update and many more features will be added!