We do both individual and cooperative team play. Sometimes it is a mix of who is on that team, but it hasn't been that staked out about "who's the boss?", etc.
On the one hand, Joe has his PC married and living in an estate in the center of the Lawful city whose province we started the campaign in. On the outskirts is his pre-marriage estate with apple orchard and half of the 500 manned militia we collectively have on the payroll. Joe pretty much takes care of the running of both areas, but I think he leaves each up to NPC control for the most part. That means he isn't learning how to do it him self, but the NPC rules are fairly reliable so we've learned as his trust in their alignment and loyalty. I think the PC's wife pretty much controls the in town stuff and his brother the outlying estate 2-3 days ride away (I can't recall the distance exactly).
As for other stuff, we kind of inherit it and let it go away as we conquer, move in, and leave. Of course this includes portions of the game world suitable for encampment (as ubiquituous as that means), but it mostly means taking over a part of an underground dungeon and defending it for rest, a safety spot, etc. In the city above "the black tower" has had the 4 archmages flee and some ex-player PCs, followers, and NPCs are running it now. Or not, it may have disappeared since then. I'm not up to date on on all the ongoings of the campaign anymore - especially the intricacies of the archmages. The tower had been a rallying point in the city and a frequent place of fortification. NPC appentrices were taken on even though the upper levels were blocked off to us.
All in all I'd say strongholds are just anywhere the group decides is capable of being defended strongly. It's territory really. The organizational details of people for us haven't been centralized by building structure, so it's hard to make a division.