Just before I start writing, I figured I'd let you know that there is a "Public Speaking" proposal lurking around on Area 51 if you'd be interested in that. It's been trying to get off the ground for a while now I think.
My general test to figuring out if something is on-topic is to ask the following question:
- Is this question about interacting with people in a specific situation?
It's a very simple question. Navigating social groups, cultural differences, complying with social norms, understanding actions... These all are ways we interact with other people.
Let's take a look at each of these points:
writing effective speeches
I'm not actually sure about this one. You could ask about how an audience would respond to a certain statement, or something like that, but the actual act of writing I would say is off-topic. There is a Writer SE for what it's worth.
speaking techniques (wide range included here - audience engagement, confidence in front of audience, etc)
Yep. No question about this one.
help with LAMDA exams
I've actually never heard of these exams, but from what I can gather, they seem to be like "applied" projects where you work together. Questions stemming from the interactions from participating in those would be on-topic.