You want to track newsletter signups to see them in reports, but you want the bidding algorithm to focus exclusively on optimizing for purchases. How should these conversion goals be configured?

To optimize bidding for purchases while still tracking newsletter signups, you should set purchases as an account-default goal. This tells the bidding algorithm to focus its optimization efforts on achieving purchase conversions. Newsletter signups should be configured as a secondary/observation goal. This allows you to track and report on newsletter signups, but the bidding algorithm will not actively optimize for them, ensuring your budget and bids are directed towards your primary objective of purchases. Setting both as secondary would mean neither is optimized for bidding. Setting newsletter as account-default would cause the algorithm to optimize for signups, not purchases. Setting both as account-default would confuse the bidding algorithm by giving it two primary goals to optimize for, potentially diluting performance for purchases.