I don’t have any suggestion for a plugin to do that. You may be using un-attached images for featured or slider, or agent, or testimonial. There is no way to separate what is used or not from un-attached images. You would have to delete manually what is not required anymore. It’s the best idea I have.
Also, you can increase storage. Nowadays hostings can offer TB or storage, so this space should not be an issue.
And you can install a plugin like Resize Images on upload so you set the max size (and not allow adding images larger than needed). 1920 max width images covers all resolutions.
Hope this helps.