Thank you. Maybe when my polish is stronger I will fully get the nuance. In my previous answer, I should have said that this is one of the frustrating things about translation. Ideas don't always translate neatly. It takes time to develop a feeling for a new language, to think in the target language. I have a long way to go in polish!
jak? means "how"- it is a question for adverb, or a description of activity,
co? - is a question for a noun, a subject that is not a person.
jaki/jaka/jakie/jacy are questions for adjective. it "what is it like", or "what kind of?", a description of a noun.
"który" is which - a question of clarification,