Hello Prophoto,
Regarding your questions.
– Yes, you can enable any folder in your joomla site (included cache folder) in sync profile settings, so static files in these folders will be uploaded to S3 bucket and served from CDN. Cron job should be enabled to make it uploads the file automatically or you need upload files manually in back-end.
– CDNs are usually geolocated, so the requests will be served from a server nearer to your visitors typically. this is the way that CDN helps your site load static files faster.
– For reference, you can find some helpful information in this slide
http://www.slideshare.net/carson3511/joomla-content-delivery-networks