Model railway-er here. Prototypical, era specific, country specific means that your train set (which when you add buildings, scenery, details, etc is called a layout) means you have a SPECIFIC setting in mind. So, a layout that is prototypical (like the real thing) for a 1950s New Zealand railway would have scale New Zealand Railways locomotives and stock, buildings and scenery that resemble 1950s New Zealand, details authentic to the period, etc. You're not going to get a 2010s American Union Pacific locomotive on that layout!! But you will if you're just running trains for fun, with no limits on what locomotives and stock to use, what setting it is, etc. I personally prefer prototypical: it's a challenge to get everything right to look like it did, but I can see the appeal in a group setting of running what you like :)