Best Fermentation cap?

[darkalex]

I just brewed the Flanders Red from BCS. I fermented the primary beer with a vial WLP001 and as activity slowed I racked to secondary, added the oak cubes, and the Wyeast Roselare blend. My questions is which airlock should I use? Right now I'm using a carboy cap. Is this ideal or should I stick with the airlock and top off every few weeks? I got a really good feeling about this beer

Thanks a bundle