The choice between Kanthal or NiCr comes down more to deck space, power available and ramp up time.
Compare
http://www.steam-engine.org/coil.html?p=roundmulti&r=0.3&hf=280&str=2&awg=26&id=2.25
vs
http://www.steam-engine.org/coil.html?mat=n80&p=roundmulti&r=0.3&hf=280&str=2&awg=26&id=2.25
this is a clapton build I did from my brother for an RBA mini deck. Notice the NiCr is almost 2 wraps longer (+4 loops) than the kanthal ... 10 loops vs 14. It also uses 38W (kanthal) vs 50w (NiCr).
The main usage for NiCr vs Kanthal is if you have to meet a lower resistance. 6 wraps NiCr < 6 wraps Kanthal.
For clapton, you are correct, the wrap wire is negligible as far as resistance goes, so ignore it. Calculate the core wires only.
TC mode should ONLY be used with factory coils. Hand made coils, there is no need. Reason.. hand wrapped coils are larger so SS requires an enormous amount of power to heat, when you can get the same result using a kanthal core and SS wrap, since it is the wraps trapping the juice.
This also greatly reduces the amount of vapor. Since SS has such a low resistance, it takes much more power to heat and much longer ramp up time than a resistance wire, such as kanthal. SS is conductive.. conducts heat Kanthal is resistive.. generates heat. Kind like like hand brakes on a bike when the rims are wet or dry.. wet rim being ss and dry being kanthal.. the friction of the pads allow you to stop much faster with more resistance. (dry rim)
In practice... I can build a quad fused clapton kanthal build that runs at aprox the same wattage as a smaller dual SS build.. more coil.. more vapor. More wraps=better (more pronounced) flavor.
The best way is to try all different types of wire. Pick the one you like best. My post is through trial and error and wire theory. I primarily started out with cloud chasing builds then moved toward flavors.