WordPress Custom Query Based Condition

popular_posts_query.php

<?php
$popular_post  = new WP_Query(array(
                'post_type' => 'post',
                'posts_per_page' => 5,
                'meta_key' => 'post_views_count',
                'orderby' => 'meta_value_num',
                'order' => 'DESC'
            ));

related_post_by_category.php

<?php
$cats = get_the_terms(get_the_ID(), 'category');
$cat_ids = wp_list_pluck($cats,'term_id');
$related_post_count = !empty($opt['related_posts_count']) ? $opt['related_posts_count'] : 3;
$posts = new WP_Query( array(
    'post_type' => 'post',
    'tax_query' => array(
        array(
            'taxonomy' => 'category',
            'field' => 'id',
            'terms' => $cat_ids,
            'operator'=> 'IN' //Or 'AND' or 'NOT IN'
        )),
    'posts_per_page' => $related_post_count,
    'ignore_sticky_posts' => 1,
    'orderby' => 'rand',
    'post__not_in'=>array($post->ID)
));

related_posts_query_by_tag.php

<?php
// Related post query for default post type (post)
$tags = wp_get_post_tags($post->ID);
$first_tag = isset($tags[0]) ? $tags[0]->term_id : '';
$rp_ppp = !empty($opt['rp_ppp']) ? $opt['rp_ppp'] : '';
$related_posts = new WP_Query( array (
    'tag__in' => array($first_tag),
    'post__not_in' => array($post->ID),
    'posts_per_page' => $rp_ppp,
    'ignore_sticky_posts' => 1
));
// Related post query by custom taxonomy for custom post type
$tag_terms = wp_get_object_terms( $post->ID, 'mtab-product-tag', array('fields' => 'ids') );
$related_posts = new WP_Query( array (
    'post_type' => 't-shirts',
    'post_status' => 'publish',
    'posts_per_page' => 3, // you may edit this number
    'orderby' => 'rand',
    'tax_query' => array(
        array(
            'taxonomy' => 'mtab-product-tag',
            'field' => 'id',
            'terms' => $tag_terms
        )
    ),
    'post__not_in' => array ($post->ID),

wp_query.php

<?php
/**
* custom_post_query_with_pagination.php
* Show pagination in custom posts archive (loop) by custom post query $paged var
**/
global $wp_query;
global $paged;
$temp = $wp_query;
$wp_query = null;
$wp_query = new WP_Query();
$wp_query->query('showposts='.get_option('posts_per_page').'&post_type=t-shirts'.'&paged='.$paged);