So I won't give you a full reply here, just some food for thought.
From presentations I've seen and done in the past, I'd be pretty much only for writing down the headlines and then going off of that if the topic is something you're informed about and are interested in. A full script won't look good like ever. It's mostly possible to tell someone's using a full script within the first few seconds. It won't look natural, especially not if the thing is visible to the camera. If it isn't, you'll need practice with it and it could probably work out.
For using basic talking points you'll need to think about how informed you are about the topic. If you're well informed and could ramble on about something for ages if you wanted to, use topics (like "Why is electricity important", "What is electricity used for", "Where to get electricity from", "Can a koala understand electricity"), then talk freely about that topic and move on to the next one. You're writing down the skeleton and your brain fills in the flesh.
Also useful (which is what I've used for presentations in the past which works good for me) is to take your skeleton you've just made and describe the bones a bit. That'll mostly work out for getting things right (Numbers, corner data, etc). Now the goal here is to not write too much, otherwise you'll be back at a full script. If you're a person that likes to ramble on for ages, set yourself limits ("I'll just list the points for which electricity can be used and explain each one in one to two sentences").
Or another way I can give you that can really work out is:
Write a full script with every detail possible you want to go into, read through it and throw it in the bin. You've written the thing, it's probably moved to your head already. Now talk freely.
For discussions, personally I'd go for the moderator to have clear points what you want to talk about and everyone else having prepared but not gotten a script. The discussion will get into a flow and you'll be happy you didn't script it.
