Detail? Sure: Look at the shadows. You can tell where the Sun is by it. And look at the dust in the windshield, cleaned by the wipers... Not bad. But true: Let's make small routes? I would make big ones to run a loco like that! (The Loco is a new Diesel made by spanish works near valencia).
Mini-routes would be better for high detail because the processor doesn't have to work so hard keeping track of the whole layout.
While it's true the computer is only calculating details of a small section of the route at a time, it's still required to keep track of the basic features of the whole route and the locations of all rolling stock and industries. This allows you to check up on things in the mini-map. The smaller the route, the less unseen route has to be processed and the more processing power is available for rendering the visible sections.
We will now pause for correction from the more computer literate anong us, who are amazed that I actually believe that.
It's mostly true, though physics collisions (such as they are) and other rending stuff is done at a certain level and nothing else. If you have a train that's not in sight on a certain layout, it won't render anything of it at all. Yes, it will have to keep track of it, but that's not too hard.