Thank you very much for your detailed response. It's extremely helpful and explains a lot. I had read a lot of information before this so it's maybe a bit of a gap.
That answers a number of questions. I wasn't clear Adapt was an Authoring Tool, I thought it was a combination of both. That makes it much simpler, we'll continue looking for an LMS that has the capacity to offer the functionality we need.
Regarding the video, I suspect we'll look for a 3rd party option - but thank you for the heads up around firewalls. It's not something we had considered.
I'll place an update here when we make the final decisions. It may update other newcomers.