I'm wondering why James able to define Enclave when they first shows up on Jefferson memorial.
A very good question indeed.
James might be an Enclave deserter for all we know. It's known that at least one deserter from Navarro made it.
Then again, the BoS has been probably talking about the Enclave all the time whilst assisting on Purity, and also the radio yapping of Eden... and the instant James saw them, he knew who they were.
Now, how did he know they were
still evil is beyond me.
As for the tech?
Vertibirds... In FO2 they were so "WTF OMG XD PWN" sort to speak,
three fractions wanted their blueprints in San Fran, and most sightings were pretty much described as UFOs - strange noises and lights and so forth.
Power Armor - "Hello? Anybody in there?" "Lost your heart, tin man?" is the FO2's normal nonnamed NPCs response to you wearing it.