On my regulated kanthal devices, I prefer a 2mm 6 wrap using 26g. Ohms out to 1.0ohms. I enjoy 35-40 watts on most juices.
On TC mode, I only tried and enjoyed a 28g spaced coil with 7 wraps of ni-200 using what I believe to be a 2.5mm machine screw. It ohms out to 0.17ohms on my dna40. I vape it at 450 degrees.
On my mechs, I'm still searching for the perfect vape, but I've tried a 0.4 ohm using 24g (not too bad, but it doesn't wick fast enough for chain vaping), a 0.2 ohm parallel using 24g (too warm for my taste and doesn't wick fast enough).