Does the RM186 / RM191 support peer-to-peer operation?

No, the RM186 and RM191 do not support peer-to-peer operation, as they are LoRaWAN devices. LoRaWAN architecture uses nodes which communicate with a gateway device and have no direct contact with other nodes. LoRaWAN can be thought of as a long-range star network with the gateway at the center of that star; all data from the nodes pass through the gateway and on to a network server. The gateway is effectively a packet forwarder or bridge, taking LoRaWAN packets and forwarding them on to an IP network.