Is it a good idea to create 2-3 ad groups with the same audience/keywords containing different banner sizes that you'd like to promote?
The point being - all sizes perform differently and I'm looking at the best way to get maximum sales out of each size while maintaining the CPA. With all banners in one ad group, if I reduce the bid to control the CPA, it would have an impact on sites that my top banners are placed on which is not desired. I'm planning to club 2-3 banners together in one ad group, say an ad group called top performers, which would have a higher bid than banners in other ad groups and so on.
I'm currently planning to try this with a remarketing campaign since there'd be no keywords in there. But would it work differently with a regular keyword+placement display campaign where each of these ad groups would have the same set of keywords? I guess they'd be competing against each other and then the ad with a better ad rank would show.
I'm sure people must've tried this. So, can anyone shed some light on the pros and cons of this strategy?