Hey, sorry i've never tried cushies so couldn't compare the size to anything else for you but didn't want to leave your post looking so lonely
My daughter is 15 months and around 22 lbs now and we're still using the same settings on most of our nappies (BTP) that we've been using since she was around 7 months just because she's slimmed out a lot and changed to toddler shape so you mignt find that she fits them for a while longer.
I've seen a few posts about some of the sized nappies such as Fuzzi Bunz where people have used the mediums especially from around 6-7 months until potty training due to their babies changing shape so much.
Without trying to sell you anything (promise!
) I've got a couple of these on the FS board at the moment although they are old and well loved (bought preloved by me) they are cheap and you could maybe get an idea from them? Another quite large nappy that I have some of just in case Grace grows out of her usual BTP ones is the Wonderoo V1 if you could keep your eye out for a couple pre-loved to try?
Hope I've helped a little