Twitter takes the title, image and then links, so this limits title length. Facebook takes the post content and makes it the FB post and then adds the packaged link with title, image and content. LinkedIn packages it together as a shared link and shows title, summary, and image. It’s probably best to always include an image, especially for Facebook.
Updated: Facebook is inconsistent. If an image is included in the native post, then Facebook ignores the post title completely and only uses the post content, image, and then links to native post.