Remove Parent Theme Settings From Child Theme
This definitely isn't the nicest solution, but it does work. If you find a better one, do post it here.

function THEMENAME_form_system_theme_settings_alter(&amp;$form, \Drupal\Core\Form\FormStateInterface &amp;$form_state, $form_id = NULL) {
  unset($form['global']);
  unset($form['bootstrap']);
  unset($form['general']);
  unset($form['theme_settings']);
  unset($form['logo']);
  unset($form['favicon']);
  unset($form['components']);
  unset($form['update']);
  unset($form['javascript']);
  unset($form['advanced']);
}