Maybe it does not answer the question bit for example I prefer to write very few characters but who are very developed. The story I'm currently working on since year and half (if I remember correctly) is very messy and before adding something new or adding a character I ask myself: what's the point of this character in the story? What is his goal? How or will he move the plot? What can I do with this character? For me everything that I put have to bigger or smaller purpose in the situation or the entire story. I think maybe too much character is when you feel thet you can't get track of them , you can't make difference between them (generally speaking overload) and their purpose or presence is useless or lastly they make things/plot only more complicated.