Try Threaded layout.

if you need the button and function, you can edit the forum.php from layout 1

search for

	<div class="wpforo-category" <?php echo $cover_styles ?>>
        <div class="wpforo-cat-panel" <?php echo $cover_styles ?>>
            <div class="cat-title" title="<?php echo esc_attr($cat); ?>">
                <span class="cat-name" <?php echo $cover_styles ?>><?php echo esc_html($cat); ?></span>
            </div>
            <div class="cat-stat-posts" <?php echo $cover_styles ?>><?php wpforo_phrase('Posts'); ?></div>
            <div class="cat-stat-topics" <?php echo $cover_styles ?>><?php wpforo_phrase('Topics'); ?></div>
            <br class="wpf-clear" />
        </div>
	</div><!-- wpforo-category -->

and replace with

	<div class="wpforo-category" <?php echo $cover_styles ?>><div class="wpforo-cat-panel" <?php echo $cover_styles ?>>
            <div class="cat-title" title="<?php echo esc_attr($cat); ?>">
                <span class="cat-name" <?php echo $cover_styles ?>><?php echo esc_html($cat); ?></span>
            </div>
             <?php if( WPF()->current_object === 'forum' ) wpforo_template_add_topic_button($cat); ?>
            <div class="cat-stat-posts" <?php echo $cover_styles ?>><?php wpforo_phrase('Posts'); ?></div>
            <div class="cat-stat-topics" <?php echo $cover_styles ?>><?php wpforo_phrase('Topics'); ?></div>           
            <br class="wpf-clear" />
        </div>
	</div><!-- wpforo-category -->
    <?php if( WPF()->current_object === 'forum' ) wpforo_template_topic_portable_form($cat); ?>

read this before making changes > Theme Customization

That's why wpForo has 4 layouts, you can change to another layout by your need.