There are many ways to play with it - one of them is https://github.com/nomic-ai/gpt4all . As for the strangeness, I would say it depends on the prompt (input).
More about this stuff: quantamagazine
Not sure, I have used PlantUML with C4 Model though (https://github.com/plantuml-stdlib/C4-PlantUML)
actually kinda interesting article, reminded me of Pattern Recognition book by William Gibson.
yeah, seems that here the loop goes again