What is the differenc between config_adhoc and config_edge?

The adhoc configuration avoids all use of rendezvous servers. Instead it relies on IP multicast. This works well on local subnets but it is very difficult for peers to locate each other across the Internet. If your peers will be widely distributed on different networks then it will be necessary to use rendezvous peers. Most of the peers will be configured as "edge" meaning that they are at the edge of the network and use a rendezvous to locate other peers. A few of your peers will be configured as "rendezvous" meaning that they act as the central locations where peers may find each other.