{% if craft.commerce.products.relatedTo({ sourceElement: product, field: 'productDesigner' })|length %}
    {% set relatedProducts = craft.commerce.products.relatedTo({
        sourceElement: product,
        field: 'productDesigner'
    }) %}
{% elseif craft.commerce.products.relatedTo({ sourceElement: product, field: 'type' })|length %}
    {% set relatedProducts = craft.commerce.products.relatedTo({
        sourceElement: product,
        field: 'type'
    }) %}
{% else %}
    {% set relatedProducts = craft.commerce.products.relatedTo(product) %}
{% endif %}

{% for product in relatedProducts %}
    {% include "partials/_product-block" %}
{% endfor %}