This the layout for *._items.php:

<div class="accordion" id="accordionTags">
    <?php if ($this->items == false || $n === 0) : ?>
        <p><?php echo JText::_('COM_TAGS_NO_TAGS'); ?></p>
    <?php else : ?>
        <?php foreach ($this->items as $i => $item) : ?>
            <?php if ((!empty($item->access)) && in_array($item->access, $this->user->getAuthorisedViewLevels())) : ?>
            <!--Card Start -->
            <div class="card">
                <!-- Row Heading -->
                <div id="tagRowHeading-<?php echo $i;?>" class="card-header cat-list-row<?php echo $i % 2; ?>">
                    <h4>
                        <button class="btn-btn-link" type="button" data-toggle="collapse" data-target="#collapseCard-<?php echo $i;?>" data-parent="#accordionTags" aria-expanded="false" aria-controls="collapseCard-<?php echo $i;?>">
                                <?php echo $this->escape($item->title); ?>  
                        </button> 
                    </h4>
                </div>
                <!-- End Card Heading -->
                <!-- Card Body -->
                <div id="collapseCard-<?php echo $i;?>" class="collapse" aria-labelledby="tagRowHeading-<?php echo $i;?>" data-parent="#accordionTags">
                    <div class="card-body">
                        <?php echo $this->loadTemplate('items_tag'); ?>                     
                    </div>
                </div>
                <!-- End Card Body -->
            </div>
            <!-- End card -->   
            <?php endif; ?>
            <div class="caption">
                <?php if ($this->params->get('all_tags_show_tag_description', 1)) : ?>
                    <span class="tag-body">
                        <?php echo JHtml::_('string.truncate', $item->description, $this->params->get('all_tags_tag_maximum_characters')); ?>
                    </span>
                <?php endif; ?>
            </div>
        <?php endforeach; ?>
    <?php endif; ?>
    <?php // Add pagination links ?>
    <?php if (!empty($this->items)) : ?>
        <?php if (($this->params->def('show_pagination', 2) == 1 || ($this->params->get('show_pagination') == 2)) && ($this->pagination->pagesTotal > 1)) : ?>
            <div class="pagination">
                <?php if ($this->params->def('show_pagination_results', 1)) : ?>
                    <p class="counter pull-right">
                        <?php echo $this->pagination->getPagesCounter(); ?>
                    </p>
                <?php endif; ?>
                <?php echo $this->pagination->getPagesLinks(); ?>
            </div>
        <?php endif; ?>
    <?php endif; ?>
</div>

And for the list of articles(loadTemplate('items_tag')):

    <?php
    defined('_JEXEC') or die;

JHtml::_('behavior.core');
JHtml::_('formbehavior.chosen', 'select');

$n         = count($this->items);
$listOrder = $this->escape($this->state->get('list.ordering'));
$listDirn  = $this->escape($this->state->get('list.direction'));

$articleTag = new JHelperTags;
$articleTag->getItemTags('com.content.article', $item->id);

JFactory::getDocument()->addScriptDeclaration("
        var resetFilter = function() {
        document.getElementById('filter-search').value = '';
    }
");

?>
<div id=tagtest>
    <?php echo JLayoutHelper::render('joomla.content.tags', $articleTag->itemTags); ?>
</div>

<ul>
    <?php foreach ($this->items as $i => $item) : ?>
        <?php if ($this->items[$i]->core_state == 0) : ?>
            <li class="system-unpublished cat-list-row<?php echo $i % 2; ?>">
        <?php else : ?>
            <li class="cat-list-row<?php echo $i % 2; ?>">
        <?php endif; ?>
                <a href="<?php echo JRoute::_(TagsHelperRoute::getItemRoute($item->content_item_id, $item->core_alias, $item->core_catid, $item->core_language, $item->type_alias, $item->router)); ?>">
                        <?php echo $this->escape($item->core_title); ?>
                    </a>
                    <?php if ($item->core_state == 0) : ?>
                        <span class="list-published label label-warning">
                            <?php echo JText::_('JUNPUBLISHED'); ?>
                        </span>
                    <?php endif; ?> -->
            </li>
    <?php endforeach; ?>
</ul>