Knowing the damage drop-off ranges is extremely useful, but I find it helpful only in the context of comparing one gun to another. After playing Ghosts far more than I should as a grown man with a job and bills to pay, I STILL don't know, exactly, where the 2-hit-kill range on the P226 ends. Or, how far out exactly the Remington R5 deals a 3-hit kill, or at what point the SC2010 becomes a 4hk. Often, this is discussed in terms of "units" or "meters," but even if I convert these to feet, it's harder for me to gauge this in the game. The other complication is that in real life, I could probably approximate a wall as being, say, 10 feet tall, or one building being about 30 yards away from another. But, since CoD is a FPS and really only a facsimile of real life, I think I'd still find it hard to judge distances in-game.
What might also be useful is using a few common landmarks to have a better idea of the scale of the in-game world. How long is the pro shop in strikezone? How far is Pinkie's from the garage in Octane? What's the length of the (roughly) square courtyard in tremor?
I have a dozen or older pictures that do this, not sure if it will help with Ghosts. But it does give some perspective.