how to Hide Featured Image in post?
How do I resize Featured Image differently than thumbnail in post?
1 - You can hide all Featured Images on all posts via Appearance > Theme Options > Post Options > Show Featured Image = False/OFF.
2 - Alternatively you could update the existing size via functions.php by creating a child theme and updating it there, but you would need to update the css to support this also. This option would be up to you, since it falls beyond the scope of theme support. If you do go this route, you can find the post thumbnail support starting on line 200 in functions.php and here is some information on child themes - https://themeisland.ticksy.com//article/1439/ There is a child theme in the theme-download-package that you can use as an example starting place in case it helps.
Wow!! Thank you very much!!