I did a lot of research into this for my youtube channel, and I also watched some of the Olivia Fox stuff, I think there are a few things that matter and aren't covered in the general theory, like being unrehearsed. I assumed this was covered under "presence," but the way it's described, it sounds like it's the same category as "warmth."

The main thing I noticed that makes a lot of intelligent people uncharismatic is that their speech doesn't match their train of thought. Possibly because they are thinking about too many things at once. I do this a lot when I'm not paying attention, and it makes you speak too quickly, not enunciate, and often mumble or have an unnatural tone to your voice. When you can stick to one train of thought and slow your words down until they match the speed of that one train of thought, you'll find that you naturally pick up the inflection, clear pronunciation, and changes in tone and rhythm that communicate your meaning more clearly and make you sound far more confident and engaging.

It's much easier to demonstrate this speaking out loud instead of in-text, but that would be something great to focus on at the meet-up.