=>I was wondering whether it would look realistic having [B&O and NYC] coming in to a train depot but on different track.
It would even be realistic to come into the depot on the _same_ track. These RRs shared trackage at stations in many towns, and shared "union stations" with each other and other RRs in larger cities.
As for your track question, mt prference is awlays to use the widest radius track that fits the space, and even to adapt trackplans to accommodate wider radius track. This often means a simpler track plan, but IMO that's a worthwhile trade off. If you need space for more trains, add "staging tracks"
- a hidden or open yard in which you store the trains between runs. With careful engineering, staging tracks an be palced under the layout on their own level - just make the grade up to the display level gentle enough that locos can handle long enough trains up it. Aim for 3 to 4% (or less, if at all possible.)
HTH&HF
Wolf Kirchmeir ................................. If you didn't want to go to Chicago, why did you get on this train? (Garrison Keillor)