Well the WN inserst are meant to fit into your WNs soooooo that would be the logical thing to do. I have a entirely bamboo insert for my NightNotion which works really really well and a MF/Bamboo for one of my WN Pockets, that one also works really well.
But for my other WN's I tend to use a Cotton Babies (BG manufacturer) MF square with an EasyPeasy Hemp insert folded into it.
I think Bamboo towelling is more bulky than the hemp fleece as I orderd an insert with hemp fleece for my SIL and really liked the look of it compared to the bamboo I have.
Not really sure if that has answered your question though