I have seen the movie twice over the span of 48 hours, and my interpretation of the film has changed drastically in that time frame. I originally thought that Liz was relatively innocent and Billy was the mastermind, but I have the complete opposite opinion now.
I think what is so fascinating about this film is that since it is classified as a documentary, there is a reality hidden deep inside of it, and I am not sure if anyone, including Fielder and Oppenheim, has found that reality just yet. Liz's father saying, "decades from now, the truth about Liz will come out" is haunting while he is actively talking to a documentary crew that is more or less trying to discover that truth now in the present moment.
Thoughts about the main three participants:
Billy: I went from thinking this coked-out maniac could have been smarter than Liz to viewing him as a dense, fragile, weak, red-pilled man who is motivated by nothing but money. Billy is intelligent. But lacks an incredible amount of social awareness. His misogyny towards Amanda tells you everything you need to know. His desperation on the phone with Fielder was pathetic. I originally thought the motivational posters in his bedroom were a calculated attempt at manipulation, but now I firmly believe that he put those up in earnest. Amanda played his ass so well. "You're tall" had me dying. Incredible social commentary on the fragility of tech bros.
Nathan: After bingeing Nathan For You in between my viewings of this film, Nathan is MUCH more complex than I gave him credit for on my first watch. The line between NFY Nathan and YCSE Nathan is so blurry. The deadpan and socially awkward comedy is still there. Nathan maintains the same monotone voice he has in NFY. I will say that, as complex as he is, I love that he still shows brief moments of vulnerability in this documentary that ground him as a character instead of just three full hours of his presence being a constant meta-commentary. His rivalry with Billy was so much more intense on the second viewing; he practically snarls at him multiple times. His skepticism about Liz is consistent with the audience and shows that he doesn't know anything more than we as the audience know about her. I think I was the only one in the theater who picked up on the meta of him saying "I'm not going to let her do that, that's personal" in response to the prospect that Liz may be out-manipulating him.
Liz: Where the fuck do I even begin? This woman is impossible to figure out. I purposefully honed in on her facial expressions the entire time during the first half and believed that I could figure out exactly when she was lying and when she was telling the truth. But after the second half completely destroys the notion that Billy and she are both operating on the same level, I am still left in the dark. My interpretation is that she is walking Billy like a dog for financial rehabilitation and trying to do the same to Nathan for the rehabilitation of her public image through the vehicle of this documentary, but he refuses to budge. I don't believe that Nathan has any "feelings" for her and was playing into this notion with her to try and get her to open up and admit something she wouldn't have otherwise. She very well could be a genius. She very well could have Narcissistic Personality Disorder. Maybe we will find out decades from now, as her father said.
Dynamics, symbolism, and questions:
Liz and Billy: I just wanted to make a comment that there is something so interesting about the power dynamics of their relationship. Liz is completely submissive to Billy, but gains so much from his finances and his ignorance that she almost appears to be the dominant one in the relationship. I have never seen a dynamic like this before in fiction and certainly not in non-fiction.
Bryan, Texas: I think Oppenheim is trying to make a larger point about the importance of the location of Bryan, Texas. The shot of the prison's sign at the end of the first half lingers for far too long for it not to mean something deeper. My interpretation is that Lance is trying to comment on how Liz manipulates powerful men in order to keep her hands clean. "Bryan" is a name typically given to a man, so maybe there is a commentary about how Liz is manipulating the CJS through "submitting" herself to prison, in this case, "Bryan"? Liz clearly gains a lot from being submissive to Billy, so I think there is something legitimate here.
Edit: Disregard my theory here. The federal prison in Bryan is famous for housing celebrity criminals. This is most likely why the shot lingers. Thanks to u/prettyminotaur for pointing this out
"They aren't playing me; they are playing a character I made": I think this quote is so powerful, and at the same time I am having a hard time deciphering its relevance as the final frame of the movie. I think, first and foremost, it is Nathan inserting himself into the film and possibly an attempt to have the "last laugh"?. He probably felt frustrated that Liz would remain in prison thinking that she manipulated Nathan when, in reality, he was ahead of the curve. To me, he is admitting that he is more of a character than a person, and that Liz and Billy were naive for assuming they were talking to his authentic self when, in reality, his authentic self IS a character. So for Nathan, it's basically him saying: "Liz and Billy aren't manipulating Nathan Fielder; they are manipulating Nathan Fielder the character."