Set both meta_query and tax_query using wp_query->set

Just use another set() method:

if ($value['pRange'] && $value['tags']) {
    $wp_query->set('tax_query', array(
            'relation' => 'OR',
            array(
                'taxonomy' => 'product_tag',
                'field' => 'slug',
                'terms' => $value['tags'],
            ),
            array(
                'taxonomy' => 'product_cat',
                'field' => 'slug',
                'terms' => $value['tags'],
            ),
            array(
                'taxonomy' => 'pa_branding',
                'field' => 'slug',
                'terms' => $value['tags'],
            ),
        )
    );

    $wp_query->set('meta_query', array(
            'relation' => 'AND',
            array(
                'key' => '_price',
                'value' => array($value["pRange"][0], $value["pRange"][1]),
                'compare' => 'BETWEEN',
                'type' => 'NUMERIC'
            )
        )
    );
}