Does the early 2014 MacBook Air use Thunderbolt 1 or Thunderbolt 2?

No, The Early 2014 MacBook Air has Thunderbolt 1 and therefore DisplayPort 1.1.

Source : Apple Support Page


Mid-2012 and later MacBook Airs do support two Thunderbolt displays (see this document from Apple), but if you're not using Apple displays it's a bit more complicated.

You'll need to either invest in something like this Mini DisplayPort to dual HDMI adapter, a Matrox DualHead2Go or a DisplayLink USB adapter (those do have issues with newer Macs and Mavericks though, I believe).