[Gandalf Parker]

In the usual glorious manner of Illwinter, the answer becomes "its different for each nation".
They are all nicely unique. Some have to worry about takeovers and sneak-ins more than others.

the Baron nation is able to create PD in towns and cities

the Witch, and the Druid, claim forests and swamps. So anyone entering them takes off the ownership. It makes it hard to sneak up on them

Troll King takes the Ancient Forests. His Mum and witch doctors can change those, and normal forests, into troll forests which generate carrion creatures. So they have a wandering PD

Bakemono generates continual new troops at mountain mines. Also the Dwarfs do if they have turned it into a colony by placing a Dwarf Queen there.

High Cultist (Chulhu/Rlyeh) creates spawned aquatic hybrids and insane peasants automatically at any seaside town or port they take

There are others but you get the idea. The ones that do not have some sort of spawned help tend to have lots of cheap commanders and cheap troops to do patrolling with. Some also have better abilities to see what is going on