Thanks! That's indeed one reason why I asked. I don't want to break the images.
CF has a service CloudFlare Images that supports Transform.
Transformations let you optimize and manipulate images stored outside of the Cloudflare Images product. Transformed images are served from one of your zones on Cloudflare.
developers.cloudflare.com
It would be nice if this plugin would transform old images and update the media URL's in WP.