Lynn Westcott authored the book 101 Track Plans way back in 1956. And yes, track planning has advanced a tremendous amount in the half century since then.
The notions in vogue in the 1950s about what constituted a track plan typically led to the proverbial spaghetti bowl - a long main line run was desirable, along with considerable industrial trackage as even then the wayfreight was appreciated.
Since that time, new notions have been grafted on as track planning has evolved. First of all, John Armstrong fathered a new breed of designers much more concerned with emulating specific prototypes. This translated into railroads that were typically around the perimeter, were linear in design and the concept of scenic sincerity meaning the track ran through a scene only once. This was accomplished in a tight space through the use of double and triple decks plus helixes and Armstrong's own invention - the mushroom.
Following Armstrong's strong influence, the NMRA Layout Design SIG introduced a great many new ideas. Key among these have been the concept of an LDE (Layout Design Element) or a domino. There has been a new found emphasis on creating specialty layouts that cater to passenger service or belt line railroads ... and considerable emphasis placed on coordinating with the Ops SIG.
While these advances were going on, two other important factors came about ... one was the introduction of modular railroads (either fixed standards or Freemo) and the other was the displacement of traditional cab control (what is called track power in large scale) in favour of the now ubiquitous DCC (battery /RC as well in the garden). both concepts have influenced greatly the way in which layout design is approached.
Are garden railroads different from indoor railroads fundamentally and therefore none of the layout design thinking matters? Personally I do not believe so. While there are many who simply want to animate their garden, there are also a large number of model railroaders who build a layout in whatever scale to model the operation of a railroad, not just its equipment. For these folks, trackplans matter ... and one would do well to look over modern layout design ideas before simply settling on a mid 1950s era trackplan.
Regards ... Doug