The word "Atman" means "higher self" which contrast with the word "deha" the lower self (Majithia 78). I believe this indicates that "[t]he Adhyatman" are the higher selves or souls. What is interesting about the word "Brahma" is that it looks very similar to the word "Brahman" which means the "universal self" (Majithia 78). While through context, I understand that this is meant to essentially be god, the implications of the idea of the universal self suggests to me that Brahma is the soul that all higher selves are trying to become. Especially since Brahma is known as "Soul of Souls" (1087) gives this idea of superiority and reminds me of the phrase best of the best.
Majithia, Roopen. The Highest Good in the Nicomachean Ethics and the Bhagavad Gita: Knowledge, Happiness, and Freedom. Bloomsbury Academic, 2024, https://doi.org/10.5040/9781350215122.
Majithia, Roopen. The Highest Good in the Nicomachean Ethics and the Bhagavad Gita: Knowledge, Happiness, and Freedom. Bloomsbury Academic, 2024, https://doi.org/10.5040/9781350215122.