Standard is good to go. The others are more costly and a bit fancier but the stock wires are designed to work with the ION sensing and more resistance will mess things up with other wires.
Never sets a code the red indicates light illuminates on the speedometer and will go green sometimes but now most the time it don't now. .
On a custom bike, you need to match your wires to your coil(s). If you are running 3 ohm coil(s), you need to run 3 ohm wires, the same for 6 ohm.
Performance bikes, yes, but mostly talking about limited-number production bikes, and one-up customs. And yes, you should match your plugs to your wires.I guess you have to run non-resistor plugs. (?)
By custom do you mean a drag bike or performance bike of some kind?.