With the AIO - you can use PUL inside the nappy as teh hidden waterproof layer and fleece on the outside. Or you can use Malden Mills waterproof fleece on the outer and not need a hidden waterproof layer.

The best absobent fabric is the bamboo fleece. bamboo velour is nice and soft for next to bub's skin. Bamboo terry is absorbent too but I find it goes quite hard with a few washes and not as good as the fleece.

The number of layers depends on your baby, the age of your baby and whether you want a day nappy or a night one. Generally (for an AIO) I would use 1 full body layer of bamboo fleece with a full body layer of PUL and microfleece or flannel (inside) and microfleec or fleece (outside), a hidden internal booster of 2 layers hemp terry. Then a snap in booster of two layers bamboo fleece with one layer hemp terry in bertwwen, topped with whatever you used for your nappy inner or microfleece (to avoid teh need for an additional liner). You would need to adjust this depending on teh factors suggested above. teh reason I suggest using a hemp/bamboo combo is taht hemp is slightly thinner so not as bulky but the bamboo has more absorbency.