I think the OP is asking is how do you determine routing as it pertains to the estimate.
Since feeders are such a big ticket item, it is important to consider the routing of each feeder on the one-line.
If the structure is 1 or 2 stories and wide open, there's not much more it than measuring lengths at right angles, up's and downs, elbows and pull boxes.
When the structure is vertical, you have to consider your pathways up through the structure, stair wells, rest rooms, elevator shafts, ceilings open to the floor below, that you cannot route through. Some structures may have a switchboard in the basement or parking garage, with panels right above the switchboard, but you may have to route 50' to a vertical pathway and back to get to that panel.
As long as the total lengths are correct after all of that, then the estimate should be accurate. How it is run in the field can still vary but the cost should be covered. And if you're lucky, if you win the bid, once you dig into the job in detail, you may find better routings in your favor