I always lower FOV as low as possible when trying to take screenshots/renders. Reason being that you don’t want dual-distortion. Your eyes already distort things, having them view something that’s further distorted doesn’t make sense to me unless you’re going for an artistic effect.
I’d recommend taking thumbnails in as close to an orthogonal projection as you can manage to pull off. Everything in a computer UI is generally “straight on”, so anything with perspective effects that gets overlaid on top (like a thumbnail would be) looks subtly “off”. In order to approximate orthogonal projection, set the FOV as low as possible and pull the camera way out so that the subject still fits the frame. The max distance you’ll be able to pull here mostly depends on the point where graphics effects like SSAO stop working. 10 degrees is pretty safe, but lower may work for you. A true orthographic projection has a field of view of 0 and the camera is infinitely far away.
Ah sorry, I thought you meant thumbnails as in like transparent icons and stuff which are meant to be overlaid on 2D UI. For an actual screenshot like this you should probably stick with the normal, larger FOVs. The one at 70 looks pretty good, although it might be worth experimenting with ones that look more like a telephoto lens, like 45 or 30.
If I do a google image search for “train”, I can see that the majority of the pictures are taken pretty close to the track (but not actually on it like your example), using a normal field of view (not usually telephoto). It looks like perspective effects are deliberately employed to make the train look longer / more visually interesting. I’m not a designer though, I don’t think I can provide much more useful input.