You or somebody has to take it apart to get to the springs...they don't just pop out.
Anyway, best efficiency is usuallys related only to the valve spring. The harder the spring the shorter amout of time it is open. Therefore less air is used. But this is only true if you have your reg properly set up to. Change your springs, then set up your reg to sweet spot it. That will produce your best results. As for the main spring, that is related to the valve time, but more so to the velocity and the different ranges that you can get. One more thing, with a lighter main spring, you can have a lower recocking pressure, which would in turn lower the amout of pressure you have on your internals and bolt. That is where he says you will see less chops.