Featured Image sizing on posts/service provider bios

When you add a featured image to a post that is then used for a service provider's bio, that featured image's thumbnail is square when pulled into the Appointments list. However, the image is then displayed at the top of the bio/post and has a very horizontal dimension. So if you have the photo fit will into a square, then it is cut off in the post. These two different dimensions are at cross purposes and inconsistent.

Is there a way to change the dimensions of the featured image displaying at the top of a post?

Or is there a way to NOT display a post's featured image at the top of the post?