Hi Elliott, This is a great breakdown and very generous in sharing your process and insights, you came a long way from the vending machine days!
Are you planning on releasing the UE4 project to the public? Or only builds? I'd love to play around with it in the editor if possible!
World of Level Design is a perfect place for you to learn about world-building in games. They do not just talk about general questions, but also share nice technical recommendations, which help to fix things really fast. In this year old article the developers showed how to find the perfect scale for your game.
2 MOST IMPORTANT THINGS TO KNOW ABOUT SCALE:
Base scale listed in this article is a good starting point. These dimensions will work 9 times out of 10.
Few things to note:
Scale and dimensions of your character and architecture is going to be relative to your game and the environment you are creating. Character collision boundaries will play a significant role for various architecture elements such as doorways height and width.
Scale and dimensions have to “feel right”. It all depends on how the player perceives your environment. So if you created “most-realistic” environment that match dimensions from the real-world but when you walk around it feels small, then you need to re-work your environment to make sure that your level “feels right”.
Remember: Everything is relative to the player and how the player sees the world.
Use these base values as a starting point but you may need to modify them to fit your project.
You can find the full article here. Plus there’s a bunch of images and a video. If it’s not enough, check out official UE forums.