The yarn is not heavy at all. Honestly, weightwise, it feels just like my hair.
Being that it is my first time doing the yarn braids, I'm not sure if I could fully answer the questions yet and would have to wait for the takedown. But from what i've heard, the yarn actually helps retain moisture better and as long as you properly take them down (no pulling or yanking, maybe adding an oil or conditioner for slip) they should be fine and you shouldn't have any split ends. HTH