Our hydro utility has established “models” of the various transmission line designs that they use. Given the system voltage, power to be transmitted, and distance involved the expected efficiency /cost ratio can be established. From that data the choice is made.

There is almost no way that the real world construction issues can be modeled at that stage because the right of way will not yet be prepped (it has trees on it and no access roads to important features)

Tower spacing is controlled by the landscape, the load bearing capacity of the towers and the wire itself. The objective is to use standard components as much as possible to reduce construction costs and future maintenance issues.

There is no question that the line will work and little or no recognition given for achieving exceptional efficiency as that is in the end more a function of the terrain than engineering.

I am talking here about British Columbia our terrain in the populated area is mainly rugged mountains.
A line built across the central plains would have virtually no terrain issues and as built efficiency should be very close to the first approximation from the “model”.

An Analogy would be pull up resistors on a port. You could spend a lot of resources and calculate them to the nearest ohm but you know that you will use a standard value as recommended in the data sheet or as dictated by your previous experience.

Should your design require such careful selection to work it would not be a manufacturable design so you should correct the design to eliminate need for critical selection .
Similarly the chosen configuration for a power line must have adequate headroom to cover unavoidable conditions imposed by the terrain.
Terry