My out and at work setup is a iStick 40W TC with a Kanger Nano tank using the Kanger 0.15 Ohm Ni200 coils. It produces more than enough vapor and taste for me, in a easy to carry package. I am vaping that at 470 degrees right now.
I also have Aspire Triton, Altantis 2, and Triton 2. I've used those on my iStick 40 TC mostly with Aspire Ni 200 0.15 coils and it works great also. In addition I've used many of the other Aspire coils on my 40 TC without issue.
Getting the correct Ohm setting locked on the iSticks is more problematic for me, than say with my Sigelei 75W. The base resistance needs to be set (locked) with the coil cold. The resistance rises as the coil heats.
If you have an Ohm meter I check the coil with that, then verify the iStick is locked at the correct resistance.
I've read that the iStick 40 is not real accurate in TC, but it seems to work pretty well for me.