Well....the answer - how long is a piece of string? There are so many variables: computing power, size of line, graphic settings, DLC types, weather effects and so on.... Firstly, let’s get a couple of things sorted, if modern is your thing, fine - modern UK railways don't have a lot of 'stuff' hanging around. Populate your line with a couple of passenger trains here, a freight there, in a few stations or yards and it can look authentic, but for us old steam fans unless you're running a small branch, you can never hope to put out the amount of stock that populated lines in those times. Take a look at pictures of Newton Abbot shed, for example, back in the day, - stuffed with locos, it had a roster of eight 51xx s alone. Attempt that sort of thing in every station and yard and TS will fall over in no time. But don't despair TS has enough capacity to give an authentic 'feel' and plenty of running options. So let’s talk about the variables. 1) Computing power, honestly don't expect to build freeroams if your computer is minimum spec. You could set the graphic settings to low and run really small branch lines, but honestly - get a better computer. TS despite being aged and antiquated can still look pretty good on the highest graphic settings - check out some of the screenshots people post. I run an i5 with NVidia 1060 Geforce, not the highest spec by any means but it does allow me to run on high graphics with sufficient assets. 2) Size of line - run a small branch for example Falmouth and with a computer of average spec and the limitations don't materialise (that often anyway). You can pretty much populate the line with as many wagons, coaches and plenty locos with graphic settings max, but once you're on the bigger lines, Woodhead for example there will have to be compromises. 3) Graphic settings - there are so many options, borderless, less complex shadows, distance blurring etc. all have an effect but most don't amount to a hill of beans - just because you've taken the distance blurring off and knocked down shadow level, don't expect it to give you the capacity for those four extra locos you wanted. The two big ones in regards graphic impact are scenery density and scenery detail. These make the big differences. The issue with scenery density however on anything other than max and it can leave out some important buildings: bridges, loco sheds, goods sheds. Taking down scenery detail however IMHO is an acceptable compromise, one notch down and the buildings aren't as good, but once out in the country you can't tell. 4) And finally asset diversity - locomotives use most 'space' followed by coaches and then wagons - but it's not as simple as that. For example if you limit the diversity of stock to only a few different sorts of wagons and coaches you'll get so much more on, but for me, it has to look authentic so if I want to create realistic steam period freeroams, I use assets of many different kinds and from many sources. So can you at least give us some sort of rule of thumb on how many assets we can use in our freeroams you say? Well as I said, my PC is i5 with 1060 NVidia. Using Riviera 1950s (a medium sized line) with all graphics set the maximum (other than scenery detail which one notch down), all graphic options on, I can run 10 locos, 50 coaches and 200 wagons. It is pushing the limitations and F2 gets a regular press as I play, but the occasional crashes don't spoil the running - a couple of locos less, fewer wagons or less diversity would make it rock solid. Finally...whilst this amount of stock is nothing like the amount that would have been around back in the day on a line such as the Riviera, it's good enough to fool me and gives pretty limitless running options - indeed I only stop and amend the scenario when I want different weather or want to bring on some different locos or wagons or coaches.
