The better UI(and paid) version drops on Steam 6th of December. Probably the best time to give it a shot.

And it is not "just" randomly generated. For example, the rivers flow where there are rocky paths in the terrain

Rocky paths are there because during worldgen game simulated erosion.

Erosion is made by simulated rainfall

Simulated rainfall depends in winds and location of a given terrain.

And only at the start of that chain there is "random generation".

> I guess I want more editorial choice in the level design.

Then tell your dwarves to build what you want, you can make pretty grand scale things in it.