OK, board size in N and other scales I've done, here's a rough guide to the size of 1 baseboard in each scale.
Baseboard scale measurements
Real 2402.3 feet 720.7 metres
G 106.8 feet 32 metres
1/2 100.1 feet 30 metres
#1 75.1 feet 22.5 metres
O 50 feet 15 metres
S 37.2 feet 11.2 metres
OO 31.5 feet 9.5 metres
HO 27.6 feet 8.3 metres
TT 20 feet 6 metres
N 15 feet 4.5 metres
Z 10.9 feet 3.3 metres
And here's a rough list of one grid square per scale.
Grid square scale measurements
Real 33.37 feet 10.01 metres
G 1.48 feet 0.44 metres
1/2 1.4 feet 0.41 metres
#1 1.04 feet 0.31 metres
O 0.69 feet 0.21 metres
S 0.52 feet 0.16 metres
OO 0.44 feet 0.13 metres
HO 0.38 feet 0.12 metres
TT 0.28 feet 0.08 metres
N 0.21 feet 0.06 metres
Z 0.15 feet 0.05 metres
Now with that, let me say I think you should actually enlarge the layout beyond scale as measured by the rulers depending on your computer. I have seen several layouts done in Trainz that are on DLS, they are usually enlarged. I remember one done exactly to scale, the buildings were tightly packed and even though it contained few baseboards, it serious slowed down my computer. Another that was a 4 x 8 HO layout was fine but only because it contained few items. For N scale, look for an old layout on DLS titled N scale, has few items and is done by scale rulers but looks kinda odd to me.
There are examples of layouts that have been enlarged on DLS. both jkeenan and CincySouthernRwy (that I know of, may be others) have layouts under their name where the description shows they are from models but they were enlarged. Making a 4 x 8 HO layout take up 1/2 baseboard x 1 baseboard provides good results, good comp performance and looks pretty realistic to me. I have also seen a 13' x 19' HO layout that should fit within 1 baseboard by pure scale rulers done as a 5 x 5 baseboard route with good detailing and it look pretty realistic instead of like a model.
So for doing a model layout in Trainz, I would estimate somewhere between 4' - 8' HO scale for baseboard length instead of the one above as provided by Surveyor's Rulers. For N scale that is roughly half of HO so it doubles, that is 8' - 16' scale feet as baseboard length. For your layout, that's 1/2 x 1 baseboard.
If you measure in real scale, it will be REALLY tiny and too packed with impossible curves.