Nomad client server communication

It is mentioned that nomad clients registers and send heartbeat to server through RPC communication. I want to know how the taskGroups are submitted to nomad client from the server. Is it also through Rest Api or the RPC call.

Also Nomad server has the UI for it. But i did not understand the reason for having nomad client UI? This seems to be exactly same as server. If it is not required can we disable it?