Craft CMS Redactor formatting I am wondering the way to go about modifying the redactor formatting settings either for all the configs or on a per config basis. I want to add custom formatting styles and classes for various text elements. Per the documentation 
it seems I need to add it with JS (not something I add in a config json file) but i'm not sure where I need to add the file.
You can use JavaScript to edit the Redactor settings, but the correct answer here is to add the settings with JSON config files. Those should go into your /craft/config/redactor folder.

Take look at the Redactor Styles plugin though – it will add a couple of textareas to your CP for adding custom Redactor JSON and/or CSS, which should make this a bit easier.