Also if you care about efficiency - did you try Effective mode? It place drills that respect it's mining area. I designed it especially for having less wasteful machine use.
I apologize if I was unclear, as we seem to disagree on what constitutes a "machine", as I consider both belts and undergrounds to be machines.
The wastage I'm referring to is not in the number of drills, but in their support structure. When tasked with using power poles, you would assign each drill pair their own power pole and set of underground belts. The only way to get any sort of power placement that acknowledges the amount of coverage is to use substations instead (at the moment, I find this to be your mining planner's unique draw over other, similar mods.)
To explain why people would want to use belts rather than undergrounds, consider the amount of materials required, vs the distance covered. Assuming undergrounds are stretched out as far as possible (to get the most use out of the materials consumed), it's only in the case of yellows that undergrounds are more material efficient (17.5 vs 18 iron plates), but that is only if you're spanning the entire 6 units of distance. Your current use is to have them at distances of 4, and then you're using 17.5 iron instead of 12.
The numbers for reds are worse. 97.5 vs 92 (or vs 46) iron for reds. Blues would be cheaper over long distances (257 vs 315 iron) but over that 4 unit distance, you only need 126 iron.
This is to say nothing of crafting time. The time for blues is 2 seconds for a distance of 4 belts while the undergrounds take 68 seconds (total) to make.
This is why people care about using belts instead of undergrounds.
(The argument for spacing out power poles instead of using one power pole for each pair of miners is similar.)
(I'd agree that once you have interplanetary logistics mastered, material costs become fairly negligible, and greens craft very quickly, but getting to this point in the game is nontrivial for many players, either because they don't have Space Age, or are just uninterested in going to Vulcanus.)