Get all fields defined in a bundle for a view mode Is it possible to get all the fields and field groups structures defined in a bundle for a view mode, in Drupal 8?
If I understood your question correctly, you need to use the entity_get_display() function.

It will return the entity view display, associated with the bundle and view mode you wanted. Simplest example:

$display = entity_get_display($entity_type, $bundle, $view_mode);