I haven't seen a new Paperwhite with 4G and less than 32gb. I bought one with 32gb because it's the only way I could get 4G. I sure don't need all that space. It doesn't hurt anything to have that room but it does cost more. I've always made it a point to have at least one 3G or 4G Paperwhite and there have been plenty of times I was glad I did. I can always load my books ahead of time so that isn't an issue but when I read I like to be able to access Wikipedia to look up things related to what I'm reading. That's worth a lot to me.
You can find used and refurbished 3G Paperwhite 3's if you shop a while but there's a risk of 3G going away so I'm not sure I'd risk that.