Who to contact?

I'd look lower on the totem pole, unless it's a short pole. EICs may not have the time for this sort of thing. In fact, better to pitch specific work than yourself unless they ask for freelance people. Whose job will it be, yours or your writing's? Check guidelines carefully and Google publications for added info.

I'm just guessing about this though.

It's better to look for the managing editor or articles editor, or the editor in charge of the specific section you hope to write for (for example, a health and nutrition editor). But as was said above, if it is a very short "totem pole" the EIC might have their hand in the selection a bit more.

What WildScribe said. You can also call the market and ask which editor assigns the subject/department you want to write for, or which editor works with freelancers if it's a smaller staff.

Be sure to follow up on your pitches and letters of interest. I usually give the editor 10-14 days to respond, then follow up every week by e-mail. If I don't hear back after three tries, and if the editor is one I'd really like to work for, I send my next query. And I rework the original query for submission to a different market.

A few freelancers I know also call the editor as their final follow-up. Can't hurt!

Good luck to you!