you can have as much locomotives as you want in any place of the train. you can also mix steam, diesel and electric engines. train length also doesn’t seem to be limited, i’ve seen trains three times as long as stations.
Not sure about lakes and such Geoff. It’s a bit of a challenge with games like these. Water only appears below the “sea level” like in Railroad Tycoon and TTD. We’d have to be able to put down some canal systems ourselves or the engine would have to have support for water as an entity, not just something that appears below a certain height.
(Most games that have multiple height support for water uses “boxes of water” shoved into the open space where water is supposed to be. It’s not actual physics as such)