I obviously can’t claim to ever have been in the cab of other than Danish trains. However on the Autostrada Del Brennero there is a particular spot (in Rovereto if my memory serves me correct, it’s been 1 1/2 years since i last drove there) where you can look right up at a straight line of railway from the car window. And at that spot you can at least tell the signal aspect from 800, perhaps even more, meters away even in bright daylight. So i would say, go for readability at least on an 800 m distance.
I think developers have different ways of solving this. Schuster signal lightglows are particularly nice. RSSLO has another solution which, not surprisingly is less elegant to watch, but highly effective for reading signals at distances.
I think, if you are thinking about making more tsc content, which i VERY much hope you will, this is one of the things where the first route would be a good practice in order to nail it. I can only speak for myself ofcourse, but signals is one thing where if they are hard to read at a distance, it’s not as comfortable driving in tsc in comparison to routes where they are easy.
I might have a couple of videos to demonstrate if you want to have some inspiration.
Another thought. Totally unrelated. The more i drive Torino Novara, the more i think it’s the best use of vegetation on track near fields i have ever seen. It feels so very very detailed and lively because you made the effort not just to go the easy way and make do with a ground tecture, but to put full vegetation (grasses, corn etc) on the fields.