Re RMS: This stuff is tricky. I don't blame folks for being confused.
If you're powering a resistive load, AC RMS and DC are identical. Line losses are the same. The resistance in the wire is no different than the resistance in the load. The losses and power dissipated in both of them are the same for DC as for RMS AC.
This is true as long as the current waveform is sinusoidal. Yes, the loss is doubled during the peaks; but it is zero during the zero-crossings. The losses averaged over a complete cycle are exactly the same as for the DC case. This is the whole point of using RMS values for AC.
Now, if you're powering some *bad* load with a high crest factor (like a non-PFC switching power supply), the current is *not* sinusoidal. It has a drastically higher peak, and then is zero for most of the rest of the cycle. In this case, the line losses are indeed higher.
As for skin effect, it is negligible at 60hz. It only matters if you are dealing with high frequencies, or huge non-stranded conductors.
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