This video gives you an overall idea on how you can start with a tool that takes a box/blockout to a building. Houdini Level: Intermediate
Some time ago I made this tool that works in Unreal Engine 4 and take your blockout and makes a final Sci-fi building from it. https://www.artstation.com/artwork/xz5WkW With this video I want to show that with a simple setup you can do the same and start exploring this idea as well. The Labs Building generator is a great way to demonstrate the idea. Even if you are not familiar with Houdini you should be able to use the Labs Building nodes. More experienced users can build their own build generator and go as far as they want.
Art refenrence from Star Citizen. Quixel Assets were used in the scene. Feike Postmes/Square Enix Research Project: https://feikepostmes.com/procedural-buildings/