I have noticed that for different countries within the same ad network, different angles and background color can work better. Which leads to the next question, do I have to test even more variables? I noticed that some cdn can work better for certain countries, as well as a certain affiliate network.
Does anyone have the same experience? And this presents a problem with scaling, do I have to do the same process on a different ad network? Maybe they specialise in the same country but different cities which have different preferences.
There are no shortage of variables in mobile.
Should you split-test CDNs? Sure, but ideally you would instead monitor page load speed and take action when the load times were above your expectations.
As for angles/background colours... the success of these will change between ad networks because placements have changed. Should you test things on new networks that you have already tested elsewhere? Certainly. But you can focus most of your testing on things that are already proven.
Different affiliate networks will do better/worse in other countries due to tracking infrastructure and the redirect process, you should definitely split-test in new countries unless one network was the stand out across the board...