First off Session isn’t peer-to-peer.  It’s peer-to-node, working like a crypto-powered Tor.

Second, SimpleX is closer to peer-to-peer with group chats requiring each member to crypto-handshake with the other ones, which is why it doesn’t scale.  Our group chat has 230 or 250 people depending on whose client you’re looking at, because the handshakes aren’t going through to all members.

Third, Session’s unique DNS enables it to hop from device to device if the server’s location is discovered, making it completely separated from physical locations.  We’ve created original server-side code for this, which you can find out about here,
http://simplifiedprivacy.com/uncensored