Thanks for contacting us here about this extension.
1) Will the wordpress media library be stored only on the cloud or on the server and cloud?
At the end, files will be stored at Cloud server. That's the reason we develop cloud integration. It helps free up your server space.
2) If it only stored on the cloud. Will any links in the wordpress blog need to be changed?
Local folders and cloud folders are two different areas. The urls of your uploaded images can not be switched to cloud links. So only the new images uploaded through cloud folders in our plugin are cloud urls. And it could be private or public links following your settings.