Hi Guys - If I store all my attachments on S3 per this guide - https://invisioncommunity.com/4guides/advanced-options/server-management/configuring-amazon-s3-r230/

And I enable "Serve images from local server" in the Remote Images options

 

 

 

Question: Will all the images stored on S3 be served from my server as well?

Pretty sure that the setting only applies to remote images from other sites (like Imgur).  There's probably a file storage settings specifically for remote images to save to local server or S3. 

Joel is correct.

There is a file storage configuration to control where the "proxied" images are stored (so they can be stored on S3, or stored locally, it's up to you). This only applies to images that are linked to when submitting a post basically (i.e. not images attached to the post by uploading them).