When you update a app on a iPod does it cost more data on your storage?
updating means downloading additional data, therefore if you!re not on a free wifi or unlimited data plan, it may cost you a bit. And generally, updating will increase the footprint of the app in your ipod for sure.
Depends if it's a utility update that just fixes issues and makes it run faster no, it just overwrites old code. If its a content update then yes it adds more features and takes up more space