$renderer = Drupal::service('renderer');
$renderer->addCacheableDependency($variables, $referring_entity);

function hook_preprocess_paragraph(&$variables) {
  foreach (Element::children($variables['content']['field_your_field']) as $index) {
    $child = &$variables['content']['field_your_field'][$index];

    if (your view switching logic) {
      $child['#view_mode'] = 'your_new_view_mode';

      // Update cache keys
      array_pop($child['#cache']['keys']);
      $child['#cache']['keys'][] = $child['#view_mode'];
    }
  }
}