Based off actually taking the drywall down, it is a crapshoot - I see plenty of jobs where you can tell they didn't care, some has been demolished by mice, and others was done pretty good.
The best insulation job I saw was wool in an 1879 remodel I completed (4" deep in walls and the same for the attic) - as for when it was installed, that is anyones guess - I didn't see any holes in the plaster or wood siding
Floors - unless it is a mobile home it generally is not installed in the south
Attics - depends on if they added more or not, but generally you might have 3" or so of cellulose for 70's & up - most in the 90's have about 6"
Walls - r11 to 13 based on age - generally all grade 3 or worse
As for vinyl siding & the r1 fanfold, I have yet to see a job done right & many jobs without it so I would strongly suggest you don't add it when calculating the values.
1954 Tract house, Pleasant Hill, CA
3 inches of cellulose in ceiling from 1980.
Low E, 2 pane vinyl retrofit windows a few years old.
No insulation in walls or basement/crawl
1923 central Berkeley one story two bed, one bath.
5 inches cellulose in attic. No wall or floor insulation.
New 96% efficient furnace with leaky new flex ducts with registers falling off into the crawlspace.
I keep on finding balloon framed walls in Annapolis pre-1950 homes. Yesterday I showed the homeowner what they look like inside with a flashlight and a mirror. We peeked up and saw the plaster mooshed (technical term) through the lath all the way up sixteen feet to the attic. The day was hot, the sun was shining and the little holes by the children's toilet were dumping 120 degree air into that second floor 'hole!' The A/C cranks all day and fails to keep up. They pay for the coolth but don't get any appreciable relief.
"Poor kid" I said to his mom. She said that winters are worse. "He literally freezes his ass off!" All I could do was suggest high density insulation or a batt stuffer job ala John Krigger with plexiglas and a seal of foam top and base. What good is R-50 in the attic if the oil-fired boiler dumps most of its expensive heat through baseboards and straight up the wall cavity?
I often probe a wall cavity with my plastic probe, and in 60s and 70s houses in Maryland, I find an occasional R-7 and an occasional R-11 but often nothing but convective currents whirling away. It's a sign of the times, a reflection of attitudes in housing, energy and lifestyle. It was easier to turn up the heat/air if comfort became an issue when it was 20 degrees or 100. What gets me is the absolute pointlessness of flopping an R-7 into a 3 1/2" wall cavity. It is about as helpful as walking into a winter storm with your parka unzipped and flapping in the breeze, but I find it all the time. It makes one wonder "What were they thinking?? Or were they?"
Another similar common find is over the garage, under the master. Often the insulation comes nowhere near filling the cavity. Over time it has sagged away from the floor at least three or four inches and this non-contact essentially renders it useless in maintaining comfort in the room.
A third common issue is the tumbling floor insulation, sagging down with moisture and gravity and often plopping right down on the crawlspace dirt. Tiger teeth fail both when compressing the insulation tight up against the subfloor and also when they get turned upside down and sag and open up a big gap between the insulation and the subfloor.
I even saw tiger teeth in a flat attic one day in a multi-million dollar McCastle on the waterfront. Someone had mooshed the R-30 batts with tiger teeth between the joists!! This mooshing had pulled the material away from the joists a couple of inches at the top and maybe an inch down as far as an inch away from the sheetrock, effectively reducing the insulation rather significantly and exposing the joists almost completely to the temperature and humidity in the attic. "Where are those brown spots on the ceiling coming from??" After I found the tiger teeth degrading the insulation and exposing the joists to 130 degree summer air in the swamp at 90% humidity, I showed them how condensation could occur on that joist being cooled from below (A/C) and sitting all exposed in the roasting attic. The celing joists were being used to 'drain the swamp' as they became vertical condensing planes, and the brown spots were lined up in parallel stripes 16" OC, thanks to an insulator's tiger teeth.