WhatsApp does, atleast their doc says so. https://faq.whatsapp.com/en/android/28030015/ ( So as we’ve introduced more features – like video calling and Status – we’ve extended end-to-end encryption to these features as well.)
Yes, but like most of these, that's really to do with the fact that E2E is part of the WebRTC spec, so anything built on it is safe for audio & video... the main advantage of Signal here is not leaking all your metadata.