Jitsi Meet is also an excellent web-based video conferencing tool. They also have a basic comparison of WebRTC vs Zoom [0] which is actually has the same demonstration video as your second article. I posted a basic overview elsewhere in this thread [1], and I would strongly recommend it.
It's free. It has apps for iOS and Android and you can also phone in. I've never used it for such large meetings, but apparently it handles 100+ people fine [0], and they have a blog post about scaling [1].
[0]: https://jitsi.org/news/a-simple-congestion-test-for-zoom/
[1]: https://news.ycombinator.com/item?id=20390149