Hi Wes!
Thanks for your patience as I discussed these with our team. Answers are below.
The new pro version will identify duplicate images within the post content, remove the duplicates, and relink the image references?
>> Yes.
Does that work for both attached and linked images?
>> Linked images, absolutely. For attached, are you referring to inline images within a post/page, as opposed to WordPress’ old “attached” feature? If so, the answer is yes: image URLs will be replaced in both src and href attributes.
Does it handle resized images?
>> Yes.
How does it handle resized versions of the same image?
>> MDD Pro will replace resized versions of smart deleted images ONLY if there is also a resized copy of the replacement image of the same size. If you have two copies of the same image at wp-content/uploads/2015/02/image.jpg and wp-content/uploads/2017/07/image2.jpg, and you smart delete the copy from 2015, then URLs like wp-content/uploads/2015/02/image-640×480.jpg will be replaced with wp-content/uploads/2017/07/image2-640×480.jpg, as long as WordPress has previously generated a 640×480 copy of the image from 2017.
How does it handle metadata like titles and captions? My preference would be to optionally merge data with an optional preference for earliest or latest.
>> MDD Pro doesn’t currently provide an interface for merging titles and captions, but when you smart delete images, you choose which copies to delete and which to keep – so you should keep the copy with the best/most accurate title and caption. However, the plugin will NOT modify title or alt attributes of existing tags, or text within existing [caption] shortcodes, in post content. It will only modify image URLs and IDs.
Hope this helps! Please let us know if you have any other questions.