Is this true: "At over 700 Hz, current simply flows over your body"?
Skin Depth
The human body does have a "skin effect" but it's not as thin as you might think.

Electric currents are confined to the outside of a conducting body, but humans are not very conductive, so the fields penetrate quite deep.

The best example that comes to mind is 2.45 GHz - we all know that a microwave oven cooks about 2 or 3 cm into a piece of meat - this penetration depth is closely related to the skin depth.

The primary reason that you don't feel high frequency current is that the nerves and cells can't respond to anything above ?about? 1 kHz. I've discussed this in a previous answer, more about the safety aspects than the skin effect itself, but it might help.

Nerve effects are the primary cause of injury due to electricity, mainly the heart of course. If the frequency is high enough that it can't influence the nerves, then all you have to worry about is the heating effect. For a potentially lethal 100 V at  20 mA, only 2 W is dissipated in the body, which is insignificant compared to the 200 W of normal body heat (though it will be concentrated at the entry and exit points). So at high frequencies you can carry a much higher current than would be lethal at low frequencies, possibly without pain or injury.

High voltage and lower current
It's not true that the current is lower at high voltage. In fact, a higher voltage will usually cause a larger current to flow, than a low voltage. High voltage overhead transmission lines might be 400 kV but they also carry hundreds of amps.

When it comes to human safety, higher voltage are almost always more dangerous.