I did NWT and est at about the same time. It was a very stressful time. And I was very unstable. I'm bipolar, and I was teetering between mania and depression. And between anger and self-hate.
From NWT, I mainly got that I was chronically insecure and fearful. And that I covered it up with aggressive edginess. I still get like that sometimes, but I'm never as unconscious about it as I was pre-NWT.
It's hard to summarize what I got from est and Landmark so glibly. A key piece is that the voice in my head isn't me, but rather stuff generated from the machinery. And that listening to it just gets me more of what I often didn't like getting before. So I learned to thank myself for sharing, and then to get in touch with what really mattered to me. As they say, my principles and values. As opposed to the ideals and standards that I'd been programmed with.
I also got lots of training in how to get stuff done. Promises and requests. The importance of tracking progress and performance. The concept that being comes before, and is the key to, doing and having. The stages of projects, and especially the idea that the relationship between effort and results is hugely nonlinear.
Edit: Also, I did NWT for maybe 2-3 years. But I did Landmark actively for over 25 years.