100W at 12V makes for a load current of 8.333A.
If you use 18 AWG copper wire, on a 1 meter run, you would see a resistive loss of about 0.349V from the wire (that counts the loss from both the positive and negative wires, 2 meters of wire total to make a
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These high end seasonics have modular plugs and a single rail -12v. Buy a smallish spool of "lamp wire" that's 16 awg and some barrel connectors at your DIY shop of choice. Order a 10 pack or whatever needed of barrel connectors with wiring from digikey for super cheap. Cut the <= 18 awg sides short to reduce loss and clamp it all together. Benefit of using all of the available -12v w/o use and added cost of any adapters.