I think the term braid is the way it weaved together, not braid as in braid we used for fishing. Nylon is the stufff to use, it gives and it sinks, multiplit just gives it a stronger rope with smaller diameter, that's all.
If the boat drags with a 60lb anchor, it's almost defo a wrong type of anchor for the ground you were anchored to, or maybe not enough chain and/or too short rope.