Once you've connected WP Media Folder with Amazon S3 you'll be able to send all your existing media library to your S3 bucket. All new media uploaded will be automatically and instantly send to Amazon S3 as a background process. The media you'll add in your content will be like any WordPress media, without any difference with the usual media library apart from loading 10 times faster :)
As an option, instead of coping your media library to Amazon S3 you can also remove the media uploaded from your server (and keeping them ONLY on Amazon S3). This is a real WordPress media library offload.
From the WordPress Amazon S3 plugin configuration, you can: Create - Delete - Select - Select location of the S3 bucket where you want to store your media.
Sending all your media on Amazon S3 without any local copy is a performance choice but what happens if you want to remove the plugin or change your media location? There's an option for that, you can retrieve your media from Amazon to you media library. All former link added in your content will remain in place (no broken link) while all media will be stored back to your server.
Amazon S3 is one of the world fastest web media delivering service used by companies such as Netflix or Airbnb. Amazon S3 has also a very high availability (99.99%) and is a low cost solution for large media library as the price is based on usage, you can all that power in your WordPress installation!
Don't worry, you don't have to be a developer to ensure that it works :) All you have to do is create an Amazon S3 Access Keys (only takes a minute), and copy paste those information in WP Media Folder configuration. Finally there's also the online documentation and our support team is available to help you with all your requests.