I am really wondering what kind of tango movements/techniques are considered inherently nuevo.
It's totally subjective, and opinions are like . . . well, you know the rest.
Shortly after I started to learn tango, I became a True Believer in distinctions like "milonguero," "salon," and "nuevo." That's because teachers and more experienced dancers spoke of them as if they were accepted as objective reality. I didn't know any better, so I made that my reality.
Then I began serious private coaching and started throwing those words around . . . and my coach fired back, "What's the name of this milonguero?", "Which salon? In what barrio?", and "New relative to what?" I was taken aback.
She proceeded to show me really old (1920s-1930s era) handbooks and posters proclaiming the steps of tango. The depicted dancers – who'd be 120+ years old today – were having a great ol' time with volcadas, enganches, soltadas, sentadas, blah, blah, blah. Elastic arms were in evidence, though frozen in a still photo. I realized that there was nothing new under the tango sun.
I think what most of the influential "nuevo" people did was (1) make existing stuff bigger to show it off to newer, less rhythm-driven music, (2) put names on the movements, and (3) systematized teaching it. There work was mostly theoretical, not on the dance floor.
Anybody who hasn't been brainwashed by some influential writer or teacher can figure out that dancers have been tangling legs, lifting each other up, jumping in the air, spinning each other around really fast, etc. since dancing was first invented, and that tango dancers weren't special in this regard.
As my coach also said, "I think the only thing that's uniquely tango is the cruzada, and I wouldn't even defend that to the death."