As someone who still might have a '2023 take on LLMs', even though I use them often at work, where would you recommend I look to learn more about what a '2025 LLM' is, and how they operate differently?

Papers on mechanistic interpratability and representation engineering, e.g. from Anthropic would be a good start.

Don't bother. This bubble will pop in two years, you don't want to look back on your old comments in shame in three.