You don’t have to use the main featured image or home page image for social previews (among other things, they sometimes cut it off in odd ways.
Here’s how to set an image just for social platforms.
When editing a post, scroll down to the Yoast SEO section
Expand the section, click the Social tab and click Facebook
Click the “Upload Image” button near the bottom
Find or upload the image you want in the media library and click the “Use Image” button
Repeat for the Twitter section
See also: Facebook preview problems if the image doesn’t show up properly on Facebook