Hi Kay,
Using third party sites such as Feefo to collect reviews is still good practice. You can collect reviews on both your overall service and individual products with them.
Their full integration looks like the best method. As well as that, JSON is a little easier on your website so won't affect your page speed. It's usually a little easier to integrate as well.
When you use Feefo as well you can mark your site up with schema markup and include your reviews to become eligible for organic stars.
Hope this helps!
