Ultimately a bubble machine is a bubble machine. No matter how efficient or inefficient the design, you're still going to pull skimate. However, I disagree that there is no such thing as "over skimming" however. Sure selecting a skimmer that will be upgradeable to a larger system is fine, but at one point you have reached a threshold at which point any larger skimmer will not be any more efficient than a smaller one. After a certain point you are simply wasting money and electricity.
This is why I usually don't recommend that people go over 2x tank volume with skimmer sizing, especially with respected brands or downdraft skimmers. A skimmer will pull the organics out of your water, no matter the size. A smaller skimmer will take longer because less volume of liquid will be in contact with the bubbles at a time but you'll still end up pulling out the same organics.
Also, running two skimmers seems inneficient and I think Tom summed it up perfectly.