Hey! Nothing to add to other comments, but for the video issue you had. I had the exact same problem and found this solution : https://simmer.io/articles/adding-video-to-unity-webgl/
It's not perfect though, as I was working with FMOD i had to import the audio in FMOD and synchronize it as I could with the video flux... which isn't really reliable as it's web but for short videos it's good enough. I guess that if you are not using an audio middleware like me, you can even use unity's listener and it'll work.