Oh my goodness you guys.
There is no way to attach a curb chain/chin strap (We are talking about the same thing here) to a snaffle where it would engage when you pulled. You could put barb wire down there and when you picked up it wouldn't make contact with the chin. The only purpose it serves is to keep the bit from going through the horse's mouth, and yes, I use one on every
loose ring snaffle I own. Typically I just tie a nylon string down there, but that's mainly because I can buy that by the foot for the same price as a pretty chin strap, and use it on multiple bridles
It's none of my business what you put in your horse's mouth...I ride with twisted snaffles as a training tool. In a perfect world you won't ever have to leave a smooth snaffle, but hey, you ride soft in a twisted and you'll be just fine. Just the key word there being soft, soft, soft.
If it's all the same to you though, until you get a little more experience, I'd put in a smooth.