@LauraA Thank you for the comprehensive reply! These links are fantastic and so helpful, definitely gives me a lot to explore. Thanks for your anecdotal thoughts and observations too.
I'm in Australia and just starting to research the book market here - there's a great local publishing industry, but from browsing bookstores and the library we seem to import US, UK and various translated European books as well. I guess I'm just curious to look at children's books from around the world... there's so much beautiful work in the Orecchio Acerbo and Gallimard Jeunesse catalogs, thanks again for the links.
As to your question about being in a stuck place of style paralysis / slow production - I don't have experience with putting together a portfolio (not quite at that stage yet!) but I can certainly relate a lot to this part: "not having a defined approach to making images slows production". If it's any comfort, you're not alone here! It takes me SUCH a long time to draw or paint anything as I'm still learning the techniques. This comic always cheers me up when I feel things are moving so slowly: https://www.instagram.com/p/BcpcZEenDXJ/