////Without any particular basis for it, perhaps some consideration should be given to the way in which different venues contributed to the evolution of the several different styles(?), and perhaps the venues shaped the music.////

Good point. In the days before electrical amplification, I would think this was especially true. Country blues was shaped by the juke joints. You had to stomp your foot and bellow loud enough to be heard but not sound like you were just shouting. And the steel box guitars were used for more amplification and it ended up being the definitive sound of country blues.

So imagine this is true of all styles of music.

/////The similar "lore" is that ragtime originated mainly from the more or less solo piano player. The somewhat more complex structure of the music perhaps required a more rapid jump to somewhat larger combos to move the music to larger halls(?), but it never was commonly played in large auditoriums so far as I've heard. (Although "marching band" spinoffs did appear?)/////

Ragtime originated on the banjo. It melded with the jig piano style of the 1880s. Marching bands started playing it but how early is not known. They may have preceded piano because the piano appropriated the march band timing on the left hand--a straight ONE two ONE two beat--while the right hand played the syncopated melody. But it didn't necessarily have to be that way, I suppose.

////The primary "swing band" style possibly was deliberately developed for large venues with lots of dancers. The music aside, in the absence of amplification you wanted a fairly large band just to produce enough volume to be heard in a large ballroom. Most of the well known swing bands played from written notation (with breaks for extemporaneous solos(?) written in), and most of the big band tunes were "composed music," more routinely than in the other styles mentioned. Using large "orchestras" almost mandated written scores to keep "most of the players" on the same tune (most of the time).////

I would agree with this. You also have to have an arrangement book laying out who was to play what and when. The songs were the same from band to band so they trademarked their sound via the arrangement and worked very hard on them. A band was lost without its arrangement book and jealously guarded them from rival bands. One member usually did the arrangements and wrote them down. This person's job was to guard the arrangement book. When Mary Lou Williams played in Andy Kirk's band, she wrote the arrangements and had to guard the book.

/////Jazz, in it's beginnings, probably originated around the same time(s) as Swing, but more likely in smaller (but not solo) groups. It was more common for the "jazz purists" to ignore written scores (because they were hard to get?), if any existed, and play extensively "in free form." "Purists" through at least the early 50s could become violent over suggestions that "swing" and "jazz" were the same thing, or even that they overlapped even a little bit. Some, at the time, might have said that "progressive jazz" with its odd meters (5/4 or 7/9 time) and polytones (out of tune notes?) was deliberate, in order to maintian the separation.////

I've read that jazz came in three forms by the 20s: sweet, corn and swing. Sweet jazz was society dance band fare with a bit of syncopation but not too much. Paul Whiteman's band was a sweet jazz band. Corn was popular among the collegiate set and it swung a bit looser than sweet but was a subset of sweet. Then came swing although the definition is even more nebulous. I guess the Hot Five was an example of swing. Maybe Jelly Roll's 1926 recordings on Victor.

But, see, that's what I'm saying--you can't get any consensus on what constitutes swing. The only thing I can for sure about swing is that it is an intuitive feeling. It doesn't show up in musical notation.