Likely it's a one size fits all deal (low price and just the game); if you want the good stuff, you need to pre-order from us.
You could put every tier in Steam. Well, at least Weekend Smasher and Full-Time Wrecker tiers must be included.
Many games in Early Access have more than one preorder package.
Pre-orders from us do come with Steam keys now that we're through Greenlight (once we have a Steam build available, naturally).
You should put this vital info in every About section of ncg site, greenlight and early access pages, yes.