Anyway, see if enabling opera://flags/#media-windows-mf-demuxer helps for now.
For some reason by default this flag is disabled.
Installed in the "Enabled" position, reloaded Opera, and now the video began to work on twitch, vk
Windows 8.1 x64 ; Opera beta 45.0.2552.89 (PGO) x64
Also is there a way of adding websites only to speed dial without having them appeared in the unsorted favorites too?
Yes, but do note I base myself on Opera 29 for Windows. You can right click on a webpage and it should list both options "Add to speed dial" and "Add to bookmarks". Click the right option and it should ignore out the other.
My suggestion was that you don't have to use Google as default search engine on desktop - though if you were searching in Youtube that's moot (Google owns Youtube and hence would know what you searched for there). Was reading an article just yesterday where MS says Google won't allow them to index Youtube to include in Bing search results.