The Ghost Firearms Vital 9x19 Para Upper Receiver most likely will not work with the FX9 lower.
The Ghost Firearms Vital 9x19 Para Upper Receiver barrel is threaded 1/2x36.
Blowback. The barrel is not ported.
Any that fits an AR15.
I have two. Mine work great with both an AR9 lower as well as an AR15 lower with a 9mm magazine block.
The bolt lock back is in the lower, so, no it does not. My AR9 does not have a last round lock back but the mil spec one will hold the bolt back just not on last round. The adapter I have for the 223 has a last round bolt hold.
It does not have a bolt carrier group, so compatibility with Glock mags will depend on the bolt carrier group and the lower receiver.
there is an outlined box in red that states "Please note, this Complete Upper Receiver does not include a Bolt Carrier Group or Charging Handle." It is right under the " Free shipping & Free returns header and above the description.
Barrel is threaded 1/2x36.