Are my two early 2015 Mac Air's different from each other?
They are the same.  The marketing name of the Intel CPU is something they put in &quot;manually;&quot; it's not queried from the CPU directly.
I wrote a post a while back on getting the CPU architecture where I make note of this:
How do I identify which CPU a MacBook uses?
You can get the &quot;marketing brand string&quot; but then you'll have to go look up that information from Intel's website.  If you use the command:
sysctl -n machdep.cpu.brand_string 

You should get a string back that contains:  i5-5250U (I don't have a 2015 MacBook Air to run it on for the exact string).  That CPU was used on the Early 2015 MacBook Air on both the 11&quot; and 13&quot; models.
As for Hyper threading, it is fully supported on the i5-5250U CPU and see How do I enable Intel Virtualization in a MacBook Pro? for additional details on how to check for Virtualization support.