One of the benefits of using a tag management system like DTM is the ability to lighten the load on your page by moving tracking pixels into DTM. Now, simply moving code into DTM may not improve page performance- Please see the following link for best practices you need to follow to get the most out of what DTM can offers while deploying third party tags:
http://www.digitaldatatactics.com/index.php/2016/07/06/dtm-third-party/
