how to propose when editing content 2 possible media style for an image field?
You could add a separate select dropdown textfield with two options, which are the image styles you'd like, and if they select the alternate one, update the field in hook_entity_view.

 function mymodule_entity_view(array &amp;$build, EntityInterface $entity, EntityViewDisplayInterface $display, $view_mode) {
   if ($entity-&gt;getEntityType()-&gt;id() == 'node' &amp;&amp; $entity-&gt;bundle() == 'article' &amp;&amp; !$entity-&gt;field_image_style-&gt;isEmpty()) {
     $style = $entity-&gt;field_image_style-&gt;getValue()[0]['value'];
     $build['field_image'][0]['#image_style'] = $style;
   }
 }