Alright, so, let's use the book to learn about our empire! So, everyone gets 4-6 vassals. I already know I want five kings, but beyond that, I'm just going to use a dieroller to randomly figure out some totals.
Now, I think that the bears and mongols are relatively desolate kingdoms, not to mention that they have substantial nonhuman populations that are harder to sustain, so they will have the lowest population density the book suggests, at 40 people a square mile. The swamp is probably a bit more lively, so I'll give it 50 people/square mile. The southern human kingdom is excellent growing country, with 80 people/square mile. Lastly, the northern kingdom SHOULD be a desolate wasteland, but it's importing lots of food, so we'll give it 80 as well. That's 4,000, 5,000, and 8,000 families per hex.
I *had* written down the exact hexes of each of my kingdoms, but I failed to retain that document, so I'll wing it.
The bear kingdom is about 80 hexes. 320,000 families.
The Northern Human kingdom is about 250. 2,000,000 families
The Centuar Kingdom is about 400. 1,600,000 families
The Southern Human Kingdoms is about 600. 4,800,000 families
The lizard kingdoms is about 240. 1,200,000 families
Total empire size: 1,540 hexes, 9,360,000 families total.
This gives us, first and foremost, an idea of how big our settlements will be based on realm pop. So here's how our realm breakdown works:
Emperor has over 4 million families, owns a max size metropolis.
NHK and SHK own over 2 million each, so they get smaller metropoli too.
CK, LK, and BK all get Large Cities, class II markets.
Princes will then control some fraction of that, but I haven't drawn lines yet or figured out how many princes are assigned to each kingdom. Everyone except the bears can support class 2 markets even at the principality scale though, so every prince except for four controls a large city.
So that's 1 emperor's metropolis, 2 king's metropolises, 3 king's large cities, 22 prince's large cities, and 4 bear prince small cities.
That's probably all the cities worth putting on the large-scale map for the empire. We don't have to roll demand modifiers for all of them, because the trade routes are short enough that unless they're directly adajcent, they don't interfere with each other! Only the one closest to our players will matter.