Ezoic is a continuous testing platform. The ad combinations are dynamic; they change based on the traffic source, device type, and many other variables. Therefore, there isn't a single 'winning' ad combination. The combinations are constantly changing!
An ad combination that worked well in December of last year might not perform as well in June of the next year. That's why the system is continuously testing - to find the optimal ad placements regardless of time of year, device category, location, and so on.
Many publishers spend a lot of time focusing on improving the RPM of a single ad unit, but this can hurt the revenue from other ads on the page. So while you may be improving the performance of one ad, you might be hurting the other ads' performance, resulting in an overall loss.
Ezoic looks at the site as a whole, and will find the ad combinations that increase the revenue for each user session. This means that the first page of a user session might have fewer ads than consecutive pages, or vise versa. Or a user coming from Facebook will have a different ad setup than someone from organic search.
All these variables are taken into account when the system optimizes your site's ads. There are literally thousands of tests going on simultaneously in order to help you increase your ad revenue.