[electromack]

Does Wire Gage have that much importance when going from the line source of 14 gage, to the load source at 12 gage.

[Perito]

Under the National Electric Code, the wire size determines the maximum current-carrying capacity of the circuit. 12-gauge wire in households is normally allowed to carry up to 20 amps. 14-gauge wire under similar conditions is normally allowed to carry only 15 amps.

Wire always has a resistance. As current passes through the wire, some power is dissipated as heat . This is accompanied by a loss of voltage. If you have very long runs of 14-gauge wire, the voltage drop will be greater than the same run of 12-gauge wire.

[stanfortyman]

Does Wire Gage have that much importance when going from the line source of 14 gage, to the load source at 12 gage.

To be honest I have no idea what you are actually asking, but YES, wire gauge does matter.

The circuit must be fused/breakered for the smallest wire in the circuit. So mixing wire sizes makes absolutely no sense. In some cases it would create a violation, such as a kitchen receptacle circuit that is required to be a 20A circuit.