The main thrust of Robin Hanson's work is that so much of human behaviour is the result of social signalling; that is, the attempt to convince others that we possess good qualities. On the other hand, The Last Psychiatrist presents narcissism as an alternative theory; that is, much of our behaviour is an attempt to convince ourselves that we possess good qualities. I haven't read enough of The Last Psychiatrist to be able to provide a good summary of their ideas, so this will just be a short comment to raise awareness that an alternative theory exists and to discuss how these hypotheses relate.
The separation between these two theories isn't as clear as it may first appear. After all, we may attempt to convince other people of our goodness in order to ultimately convince ourselves or we may attempt to convince ourselves of our goodness so that we can more persuasively convince other people. For the later, imagine someone prepping for a job interview teaching when they are aware that their knowledge of the material isn't as strong as they'd like, but believing they might get hired if they seems confident.
Trying disambiguate using revealed preferences may be misleading - someone may spend most of their time trying to impress other people, but that may simply be the strategy they've adopted for convincing themselves that they are worthy and they may drop it as soon as they learn other strategies. Alternatively, trying to use people's ultimate goals to disambiguate this is tricky when, according to both theories, we often don't know why we do what we do. And indeed, when we talk about ultimate goals, are we referring to the ultimate goal that is represented in the brain or are we allowed to reference evolutionary psychology reasons for behaviour? Then of course these the issue that most of the time, both theories will be correct to a certain extent. I'll admit the the practical consequences of adopting one theory over another aren't always immediately clear, but I expect that adopting one model instead of the other would necessarily result in some differences in predictions.