We used bamboo and sized down. He wore the small until he potty learned at about 24 pounds.
We used them coverless, with fleece, and with wool. He was PUL sensitive, so we didn't put a cover.
If I were starting a stash for pl'ing specifically, I would go coverless or just use fleece shorties or longies (depending on weather) b/c its so much simpler than wool and (in theory) you don't need all of the benefits of wool for this stage of the diapering game.
Would do wool or a cover for night time and errands though.
Lemme know if you have more questions.
They worked awesome as trainers! Couldn't have loved them more.
Awesome feedback! Thank you. I think these will work great & cheaper than trainers!