OHLE is a conductor too. The issue with conductor rials is that they use DC rather than AC, which means that voltage is lower, meaning substations need to be more frequent. However, the conductor rail takes up no additional space in the loading gauge compared to OHLE, so for underground systems, or systems that need minimal clearance, conductor rails are better.

"Conductors" as in any piece of metal that conducts electricity? Those overhead wires are also conductors, and will see some energy loss over their length like any other conductor.