Awesome, hope it all works out.
Stack is quite simple: Frontend: Bulma.css, Vanilla Javascript, HTML Backend: PHP, MariaDB
It works by redirecting in the right moment to the streaming sites, via a JavaScript redirect.
The voice chat is done via https://meet.jit.si/
To handle potential big load, I force cloudflare to cache all sites under url /p/* thereby after the creation of the watch party, no request hits my server anymore :D