Quick questions

I found a Canadian small press yesterday in the midst of my research that seems like it might be a good fit for my manuscript; I'm not ready to submit yet, so this is for future reference.

1) If they say on the website, 'You can send a story proposal or a complete manuscript', which one would be preferrable? Is sending the complete manuscript better if it is a final draft (which mine would be) or would they prefer a story proposal? I realize that this tends to be subject to the opinions of the individual publishing house, but I was curious of the general consensus.
2) What does a 'story proposal' consist of? Is this another word for a query letter, or is this more a, 'cover letter and synopsis' type thing?

Thanks so much to anyone who can offer an opinion.

It's a YA novel at the lower end of the word count, so it wouldn't be a terrible hassle to send it. I'll see how I feel once the final draft of the novel is done. Thank you for clarifying about the story proposal!