So since I posted this poll I've been thinking that the options I included in it really weren't inclusive or organized as well as I wished they had been, and I've been trying to think of some way of better organizing the options into some kind of chart — not to repost the poll, since I can't very well post poll options in a chart, but just to sort of get my own head around the kind of data I've wanted to gather. Tonight I think I finally came up with something satisfactory:
For clarity: "Private room, shared living space" means something where you've got your own bedroom but share some other housing facilities like a bathroom or kitchen or living room; "Private living space, shared building" means something like an apartment or condo, where all your facilities including kitchen and bathroom are in your own private space but you share walls or even halls with other such spaces; and "Private building, shared land" means something like a mobile home in a park or a guest cottage on a larger land, where your living space doesn't share any walls or halls with others' but you've still got to cross someone else's property (parking lot, yard, etc) to get from the public street to your private space.
And "Own but still paying rent / fees indefinitely" means something like a mobile home or condo, where you are renting the use of the land or the shared facilities (including HOA fees, etc), and possibly interest on the loan you're buying with too, but at least some of those charges will continue forever with no possible end; while "Own but still paying interest temporarily" means the usual home loan situation that will eventually end once you're done paying it off. Neither of those or "Own with no rent / fees / interest" are meant to exclude property taxes, since to my knowledge there basically isn't any practically possible way to acquire the allodial title that that would require.
One thing I wish I could include on this chart somehow, but couldn't figure out how, is whether a given space has room enough to share willingly, as in, to have a spouse and kids or just a guest room, as opposed to barely enough space for just yourself. When I set out to make this chart I was thinking that would be the last step on the "privacy" (vertical) axis, except you could have a one-bedroom apartment/condo (private space, shared building) or a multi-bedroom one, a one-bedroom mobile home/guest cottage (private building, shared land) or a multi-bedroom one, and I guess in principle a one-bedroom real house on its own land or the usual multi-bedroom ones. And I guess in principle there could even be huge multi-person studios, maybe? Any way, I'm not sure how to include that in there.
Two other obvious factors sort of parallel to the two axes of this, which could include the "how many people do you have space for" question in it, would be size and price. But that would be a four-dimensional chart and I can't draw one of them.
So, in my personal history I went back and forth from (counting right then down from the top left) [1,1] to [1,2] for the first 20 years of my life (depending on whether my parents had space enough at the time for me to not share a room with them), then to [2,2] for the next 10 years of my life (renting rooms in strangers' homes in my twenties), and now I've jumped to [3,4] (a mobile home I own and live in by myself, but on land shared with other mobile homes, on I will perpetually owe rent until I move), and I'm desperately aiming to get to [4,5] or at least [3,5] (hell I'd settle for [2,5]) without compromising the feasibility of reaching [5,5] with enough time before I die to actually enjoy it. Unfortunately by all appearances any additional privacy in the short term would cost so much as to sacrifice security in the long term.