Now that that is all done, I am now fretting over my presentation, how I came across, and how it was received.

Very oddly - when I was done, I received only silence at first. No one said anything in response, except the hiring manager who asked me if I had also looked at the technical.That kind of bothered me since I had been asked to come up with content opportunities, but I hadn't been asked to look at anything technical regarding this website. Then, there were only a couple of questions regarding my presentation, and we moved onto a more formal interview style whereby they could ask me whatever they wanted and I could ask them questions too.

And since it was a presentation and not of the typical interview style, do I send a thank you note? This wasn't a typical interview, so I am not sure if I need to send a thank you note or not?

Edited: I sent one anyways since it feels like the right thing to do.