1866 is an OC frequency, so yes, you would have to OC your RAM to reach this setting. The voltage you're inquiring about is the voltage that G.SKILL used to during testing the F3-14900CL9D-8GBXL kit, when they set it at CL9 latency, or 9-9-9-27.
As for plug and play, well RAM is P&P, but there are default values for DDR3 (as well as lower tech). By default, your mobo will probably read the RAM as 1600MHz 9-9-9-27 1.5V. To attain the 1866, you'll have to change the [Auto] setting to [Manual], which will open more settings, where you will see the frequency setting.
Overclocking doesn't always require overvolting, but yes, you don't need to volt higher than 1.5.