Efficiency of a multi-output power supply
Unfortunately it's difficult if not impossible to answer whether the unit will be efficient at any setting based solely on its description. It's probably a switching supply rather than linear, which means it lacks a heavy transformer typical of those units. In theory, because it is a switching supply, it will be fairly efficient at any setting, but there's only one way to determine this conclusively: measure it.

Though these type of power supplies have come down in price considerably, and are so ubiquitous that they are generally taken for granted, remember that "you get what you pay for."