The ready-made nores-res-wires I used for the Sophia V1 were about 0,20 mm, it was not possible to go higher because of the ceramic cup. So with the Sophia V2, I at first tried 0,25, then 0,22. Noticed no big difference and saw no necessity to try 0,30 (but again - it is only me). So I stick to 0,22 mm now. Also, I tried coil diameter 2,5 then 2 and 1,5 mm. But 3 mm is also possible. Sorry for all this "mm", but I am not accustomed to AWG.
To sum it up:
The last-but-one was Kanthal A1, 0,22 mm, 2 mm coil diameter and about 6 windings for about 2 Ohm resistance.
The last one same wire but 1,5 mm diameter with 9 windings for about 2 Ohm resistance.
I like to use this very simple coil calculator,
it has an English version and it may help you when experimenting. There are also more complex ones ...
PS
Come to think of it, I made
some (not very professional ) pics for the German forum yesterday, they may help you to visualize what I am talking about