Hence the forum name
I own both (6 DNA40, 2 SX350j). Granted, I have only a week with the SX350j, I think the DNA40 is a better chip. Some will see this as fanboyism but from my observations and knowing how each chip works, that's my conclusion so far. How much better? Not much. The DNA40 seems to be made by engineers for engineers. The SX350j seems to be made by engineers for consumers. If you look at each chip as an engineer or even a tech geek, you can really appreciate how the DNA40 works over the SX350j. The problem is that in the real world, there are too many variables that can't be controlled by the chip so neither will shine for everyone.
My oldest DNA40 is 8 months old and used just about every day since I got it. Never had an issue with it. If you have a solid atomizer and build, TP and refinement is pretty amazing. I have the newer DNA40's with atty lock and never use it. It's a band-aid for a bad atomizer or build or even a badly wired mod.
If it's anything like the DNA40, yes. You go into temp adjustment and scroll up until you see off. I've had no issues using a kanthal build in temp mode though. It just works like non-TP mode.