1- You can choose where you want to display share links: on posts, on pages or on posts and pages.
3- You can hide some of the shared links.
4- If your article does not have the featured image random image from your pages will be used in social networks. Here you can upload an image – for example the logo of your site – this picture will be used if there are no featured image.
Use images that are at least 1200 x 630 pixels for the best display on high resolution devices. At the minimum, you should use images that are 600 x 315 pixels to display link page posts with larger images.