A brief story about designing your track plan.
I'm working on installing a short spur that will hold two cars in an industrial area. It has to fit in between a couple of other spurs, both of which are curved, and work with an existing industry.
The first plan was to install a number 9 turnout. After some review, it was determined that wouldn't work out as it didn't allow the track length needed before it hit the end of the area allocated.
The next plan had a #7 with a curve off the end of it. That plan seemed good, but it turned out there was some wiring in the way that originally seemed like it could be avoided, but it turned out it would need to be moved.
The third (and current) plan is to move the wiring, install the #7 and have the track run straight off of the turnout. The spur will be a little shorter than originally planned, but can still fit two cars and won't require moving a loading dock area.
So, for one turnout, and a single short straight track, I've gone through at least 3 iterations of possible plans. So just imagine how much more complex it is and how many options you have when you're building an entire layout!
Oh, by the way. Did I mention this is for a full size railroad, and the 3 designs were all created for us by a professional engineer/survey group who specializes in railroads? Yes, that's right, even the big guys have this same problem. (The "wiring" in the way? A light pole and junction box)