ESP32 Forum

I am using onoffserver project and need to know tat does the app decides which node should be friend, proxy, relay etc.
I am new to the ble mesh and i am little bit confused. Kindly suggest me something to start so that i could make my own project and add several characteristics to that project.

You are the one who decide about that. All options you have in menuconfig to enable/disable relay and proxy features on node.
Later you can also control each provisioned node if you want it to use each feature or not. For example nRF mesh used as provisioner has option for each node to enable/disable it.

If you are asking what part of mesh is deciding which ode will relay message, then answer is: all relay nodes which are in range to receive message will relay it and low layer mesh app will know if it the same message even if received from few relay nodes.
The same situation is with proxy.