They say that is is insulation as well as a radiant and vapor barrier.
It's unlikely you will be able to save your hair after you dread lock it. While there are conditioners available that may be up to the job of untangling dreads it's likely the damage the conditioners do to the hair and the stress of being locked for so long will damage your hair beyond repair and will look terrible when combed out. You could try micro braiding your hair. It's more expensive since you will need to get it done every month or so but it comes out much easier and you can learn to do it yourself.
Either would probably work but I'd prefer plastic. KAM plastic snaps have passed CPSIA safety certification for children's items. They're also much cheaper and the color selection is huge. Plus I think they are less likely to harm baby (rusting, some metal snaps have sharp pinchers so if they fall off they might scratch the skin, possibly allergic reaction,etc). And plastics are just as secure as the metal type.
