Context man. e2ee for the voice/video calls obviously which they say themselves isn't enabled. Although that is a bit strange as p2p browser webrtc is somewhat e2ee by default. Maybe they mean the initial key exchange or so?

An SFU is a server side component that forwards video streams and which is required to have video calls with many people. The 8 they mention with their SFU less mesh calls is highly optimistic, in reality it starts breaking down at 4 participants or less.