Howdy! I have a blog where I talk a lot about design theory. I have a bunch of posts on there that folks might be interested in checking out! I'll also use this thread to link to my new posts!
Today, I put up a post introducing a new model that i'm using to think about my design that might be useful for thinking about your design!
https://goatsongrpg.wordpress.com/2019/03/20/the-tfa-model-part-1-primer/