Sam, (Koen may have addressed this already.)
I’ve been away on vacation, otherwise I would have responded sooner.
Here’s a link to a sample video background:
http://videobackgroundexample.webflow.com/
Here’s the Webflow public link so you can poke around:
https://webflow.com/design/videobackgroundexample?preview=93af2bbb504a9de9b71b4be751c1ca8e
I followed Method 2, which didn’t need any coding:
Hope this helps you and others.
Todd