I added wp-smush-pro to www.sobeys.com hoping it would bulk

I added wp-smush-pro to http://www.sobeys.com hoping it would bulk "Smush" images and start automatically serving optimized version (i.e.: by detecting screen size or improving the size of referenced images) but I am not seeing any difference despite the plugin confirming it has shrunk files. See attachments.

If this plugin won't work how do I remove all of the images it created? I don't see any option. The media library now is barely accessible - very slow due to the size of how many images exist so I want to know if there is a way to remove them without accidently deleting the originals. I did select "Keep a backup" option before bulk operation.

We're on WP Engine if that helps at all and I've cleared our caches (CDN, page, etc.) to ensure it isn't related to that.