I have seen this behavior with even non-twisted 28ga NI200 at times. I have no idea why, but the much lower temperature setting works the same as it would if it were where I usually run it at around 420F or so. It is just lower for some reason maybe 1 out of 10 times with a build or new juice. I am guessing it may be the juice since I do go anywhere from 50/50 to 100% VG depending on my mood.
I have posted this a few times, but the way I set my temperature is working very nicely for me. YMMV. I have made some minor changes though. First I want to make sure my atty, wicking, juice is settled in. It may be a little erratic when you first build. Wicking is very important factor also. You want to ensure you have a very good connection and can test that by taking the atty on and off and you should get the same calculated resistance. It should be very close. I am usually within .001-.002 at most in variance. You MUST ensure that the atty and mod have settled in at ambient temperature before you set your baseline resistance. I can't stress this more. So many posts have come through this thread by those experiencing weird results because of this simple required process.
I usually set my temp at around 520F or so for me to calculate my desired temperature. Different juices, builds, etc. will require a different final temperature. I set my Joules at 14J and run my baselining in Standard mode. I used to use 8J but I am getting more consistent results at 14J which I find doesn't cause the SXM to cause too much PFM during firing and it is the Joules setting I end up using anyway. I hold down the fire button and watch the temperature rise and find the temp where it seems to settle down for the most part. I will take a hit every 5 seconds or so to ensure the wick is still wet. The temperature value does move around a bit at times, but you will find a number that it seems to be mostly settling in at. Then I change the temperature setting to whatever that temp value I found. Never lower, but sometimes a few degrees higher at most. You can then adjust the mode to Soft, Powerful, Powerful+, or just keep it on Standard which is probably the most consistent vape along with Soft which has a slower ramp up.
I have found that 14J or 18J, will give me a very pleasant and consistent vape with no PFM pulsing which you will get with the higher Joules. 18J also works fine, but will be slightly warmer. 14J is very nice for me anyway most of the time. I have tried going higher with the Joules all the way up to 50J, but I find that is just causing jittering, rattlesnaking, or whatever you want to cause it as the SXM just pushes too much power and the chip just needs to throttle down too rapidly to compensate for your temperature setting. If you are hearing that rattle then you your temp/Jules settings are just too high for the build.
My theory here is to let the temperature setting determine the correct value for all the variables such as atty resistance, coil resistance, wicking, juice, and all the possible things that cause one build to be different than the next. When the temperature settles down comfortably without a high Joules setting causing pulsations in temp, that seems to be the value that I want to use. With that setting I find the juice is vaporizing just what it wants and not excessively heating it so that it wastes juice by turning it into gas at the higher temperatures which it just doesn't need. So if your temperature is jumping all over the place you are not taking advantage of TC within the limits of the SXM. You may get what you believe to be a good vape, but it could be better, much better.
I have been shooting for around .007 resistance in my builds and right now I have it at .078, 14J, and 429F, using a 50/50 PG/VG juice. I have been running this all day with a few tank refills on my Lemo 2 and having some of the best vaping I have ever experienced with awesome flavor and nice clouds. I have my airflow about 80% open which gives me a great flavor and keeps the wicks saturated. I have also reduced down the drip tip on the Lemo 2 because I don't like such a wide tip that it comes with and I feel I get more flavor.
If anyone has some other method to set your values and get consistent results I would enjoy giving that a try also to compare results. Of course, you could just by magic find a magic set of numbers and get great results but what about tomorrow or the next build. Would it also work? Maybe I am being too scientific here, but that is just the way I operate and I like predictability which I think I am finding for the most part. Not 100% of the time, but maybe around 97% of the time.
I just love my SXM and all the tinkering you can do with it to find your sweet spot. But I feel this is not a mod for a newbie and will require some skills to make it work very well for you in TC mode.