Based on empirical observation, not knowledge of the agreements, the answer to you first question is it depended on the work load and the jobs could be combined. From what I saw on the DRGW ng. all the jobs west of Alamosa were combined agent/telegraphers. More generally, and this is based on my days working for the SP, depending on the size of the work load, the arrangement could vary from a single agent/telegrapher, to an agent with a whole bunch of clerks and telegraphers working for him. In the large agencies the agent might be an exempt or officer position (not subject to bid) if I remember correctly.
In answer to your second question, presumably the shipper of the car from Lumberton would take (drive) his bill of lading to the closest open office. Depending on the size of the shipper and how the shipping company was organized, the bill of lading might be delivered to a railroad agent at a very different location. At the risk of saying the obvious, it was the development of highways and communications services that allowed the railroads to close the plethora of agencies that used to dot every line, when bills of lading had to be walked to an agent of the railroad.
One of the things I find very interesting is Bob Richardson's statement that the Farmington station for some period had the highest cash reciepts of any station on the DRGW. Since virtually all the traffic was inbound, apparently the drilling pipe and/or mud was billed COD, which seems a bit strange to me. But it must have had something to do with the nature of the drilling supply business.
JBWX