On regular mode, I believe that charger only pushes .5A if two batteries are inserted at once. That's plenty low enough.
If you're only charging one battery at a time, it appears that the max is 1A. Which is fine. Going to the "low" setting will pretty much just make you wait longer for your batteries to charge.
There's a slight possibility you might get a bit more overall life out of your batteries if you use Nitecore's LOW feature, or possibly get a few mAh additional capacity out of them after each charge. But those concepts become more pronounced if you have a 2A charging capability next to a .5A. And I've never tracked down any charts from real-world testing to prove those concepts one way or the other.