I have the Gerbings as well..... I find that cranking the heat UP at the beginning, and then lowering it, as I go along, works best.... for me.
How low will YOU need the thermostat to be set? will depend on you, and that day's weather.
As far as whether you "high" setting, is the same as another unit... "high" simply means the unit, is getting a continuous flow of electrons, the "theromostats, and 3 position units, are "interupter units" in that they simply open and close the circuit, at given rates