How to call my custom WordPress Comment form without getting the comments?

Yes, You can customize the comment form with the Bootstrap 4.

You just need to do some edits with bootstrap classes and HTML.

$args = array(
    'comment_field' => '<p class="comment-form-comment"><label for="comment">' . _x( 'Comment', 'noun' ) . '</label><textarea id="comment" name="comment" cols="45" rows="8" aria-required="true"></textarea></p>'
  'fields' => apply_filters( 'comment_form_default_fields', array(

    'author' =>
      '<p class="comment-form-author">' .
      '<label for="author">' . __( 'Name', 'domainreference' ) . '</label> ' .
      ( $req ? '<span class="required">*</span>' : '' ) .
      '<input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) .
      '" size="30"' . $aria_req . ' /></p>',

    'email' =>
      '<p class="comment-form-email"><label for="email">' . __( 'Email', 'domainreference' ) . '</label> ' .
      ( $req ? '<span class="required">*</span>' : '' ) .
      '<input id="email" name="email" type="text" value="' . esc_attr(  $commenter['comment_author_email'] ) .
      '" size="30"' . $aria_req . ' /></p>',

    'url' =>
      '<p class="comment-form-url"><label for="url">' .
      __( 'Website', 'domainreference' ) . '</label>' .
      '<input id="url" name="url" type="text" value="' . esc_attr( $commenter['comment_author_url'] ) .
      '" size="30" /></p>'
    )

);
comment_form( $args );

Please use this. I think it can help.