Do you put your cell phone in a lipo charging bag? Or you laptop in a lipo charging bag, that uses uses several cells?
Would you fear driving a Tesla Models S, using around 7000 NCR18650 batteries? (Even in crash tests its doing great in terms of battery safety and everything)
Im all for safety, but after reading on BLF on li-ion safety you can easily end up getting a bit paranoid about the safety of li-ion cells in general.
How many thousands of 18650 cells do you think get produced on a daily basis? The very few cases I have heard of causing any damage have used crappy (Ultra)Fire cells, in crappy chargers, and combined with lights using a series-setup and no checking on the batteries.
There have been reports of cell-phones blowing up and such too. Li-ions are not 100% safe. Living, walking out of the house and such are not 100% safe either. Considering the amount of li-ion cells that is around, there is really no need to worry as long as you get some good cells and don't abuse them in any way.
When that is said, I prefer protected cells, because I have managed to run into the protection on some cells a few times (either due to extreme drain, not something you should worry about unless you are doing some extreme current modifications to some lights. Or due to badly designed light,possibility of tail/driver spring and retaining ring connecting to the battery at the same time. Or due to user error when trying something..
3x350mA regulators gives you 1050mA. 1 amp aint much. 18650 cells can do 1amp all day long, at least until they are empty.
Im not sure which cell to recommend you if you are going the unprotected route though. So this reply may not be that helpful, but using a single cell in a flashlight is not much to worry about in general. On top of that the nanjg 105C also have built in low voltage warning, so when using the light there is nothing to worry about, because you will be warned with blinking/dimming. You could end up draining a battery if the light gets accidentally tuned on, but if you have the light in a bag, purse or something. Just unscrew the tailcap or body a little. On most lights that cuts the connection and renders the tailcap useless for accidental activation.
I either stick to protected batteries, or high drain batteries without protection. If I use high drain, I often combine with a Qlite driver or something. That driver cuts off the light when cell voltage gets very low, but first it warns you. :) Its basically idiot proof.