An advertiser creates actalike and website retargeting audiences and wants to include these audiences in campaigns. The advertiser wants to see which audiences have a higher engagement rate and lower cost per mille (CPM). Additionally, the advertiser wants to optimize toward the top-performing ad group. How should these audiences be set up?

Creating new ad groups within the existing campaign allows for direct comparison and optimization. By placing the actalike and website retargeting audiences in separate ad groups under the same campaign, the advertiser can easily track and compare their engagement rates and CPMs against each other and other existing ad groups. This structure facilitates optimizing toward the top-performing ad group without needing to manage entirely new campaigns. Creating new campaigns would fragment data and make direct comparison more difficult. Adding personas is not the correct mechanism for audience segmentation. Creating a new campaign to find new customers is a different objective and doesn't address the need to compare existing audiences.