The Campines may like leghorns survive in confinement. I think they are very similar birds in temperament based upon your descriptions. I can tell you that without a total confinement system leghorns are excellent at escaping. Daisy, the greatest hen ever, and Elphie really helped me to refine my coop and run setup.
If I compare them to Patsy my Maran from the same time. They were much like your Campines vs BRs. Patsy would have gladly stayed in a run that Daisy would immediately escape.
I'm not saying that either of us would keep our ladies in a small confined space. I will ask this though. Campines don't eat a lot do they? How are they at laying? A lot of smaller birds are bred for egg laying, food to egg ratio being important. Those breeds tend to be kept in small spaces as well. Wrong as it is they may "bear" it well.
We both know they actually aren't. They are actually starved for engagement and living miserable lives.