Hi Uma,
Kanthal and Nichrome have different resistances/length. Kanthal is typically +10% resistance for the same length. So, on silica wicks you can get more twists with Nichome than Kanthal for the same resistance. For me, I use Kanthal on everything simply because it has a higher melting point so I pop fewer coils on ultra-LR.
On the twisted wire, resistance is a measure of how much restriction is put on the flow of electricity. Like a water pipe, the smaller the pipe the more restriction. Unlike dual coil cartos (completely independant coils - 2x 3.0Ω coils => 1.5ΩDCC) a twisted wire is touching along the whole length so you don't actually get "double the flow". It does lower the resistance to about ~2/3 (not 1/2). I haven't used twisted wires in a while instead opted for getting fatter wires. Where I used to twist 32awg, I now pretty exclusively use 28awg or 30awg. Twisted wires give a different type of flavor to me, slightly muted but also are very easy to work with and very forgiving for wrapping.
What I'm really enjoying these days is 0.6mm x 0.1mm Kanthal ribbon. I wrap it the same as 30awg/28awg: 2/3 on fat wicks and 3/4 on thinner wicks.
Let me know if I've missed the point with these responses (multi-tasking atm...)