Howdy Again
I doubt if you will find all the answers to your questions in one place.
I can tell you that as far as Smith and Wesson was concerned, they made three basic designs of revolvers over the years. The first were the Tip Ups. So named because in order to load them you popped a latch at the bottom of the frame and rotated the barrel up, much like the Remington double derringer. Once the barrel had been rotated up you pulled the cylinder forward out of the frame to load it. Then you replaced the cylinder in the frame and rotated the barrel back down again, snapping the latch into position. Then you were ready to shoot some more.
This photo shows the three different sizes of Tip Ups, the #1 at the bottom, the #1 1/2 in the middle an the #2 at the top. The #1 was a tiny 7 shot revolver chambering a cartridge we would call the 22 Short today. The #1 1/2 was a five shot 32 Rimfire and the #2 was a six shot 32 Rimfire.
This photo shows a #2 broken open ready to be reloaded with six more 32 rimfire rounds. The rod under the barrel was used to poke the empties out of the chambers.
Some of the history of early revolvers is based more on patent law than other factors such as power or material strength. Colt's patents on his revolver mechanism expired in 1857. Up until this time, all revolvers had been percussion, meaning they were loaded with loose powder and ball and a percussion cap was affixed to a nipple at the rear. (yes, there were a few flintlock revolvers, but not many).
During the middle of the 19th Century metallic cartridges were new technology. An employee of Colt named Rollin White had the idea of boring the chambers of a revolver completely through, so a cartridge could be loaded in from the rear. White brought his idea to Colt, but in what was probably the worst business decision of his life, Colt passed on the idea. Probably because the demonstration models were very crude. So in 1855 or so White patented the idea himself.
About that time Daniel Wesson came up with the same idea, totally independently of White. Wesson took the idea to his old partner Horace Smith and Wesson designed a little revolver, which eventually became the little #1 Tip Up. But when they did a patent search they discovered that the idea had already been patented by White. Smith and Wesson attempted to buy the patent rights from White, but he refused to sell. Instead he licensed S&W to produce their revolvers paying him a royalty of 25 cents for every revolver they made.
The White patent expired in 1869. Daniel Wesson was sure all the other revolver companies would be ready with their own revolver designs for cartridges, so he decided to come up with something really revolutionary to catch the others flat footed. This was the big 44 caliber single action revolver that eventually became known as the American model. It came out in 1870 and it was the first Top Break revolver. The American model was a big, powerful revolver, much bigger and more powerful that the little Tip Ups. As it turned out, Colt was busy making Conversion revolvers that converted their percussion models to cartridges, as stated the SAA did not come out until 1873. As already mentioned, the S&W Top Break system automatically ejected all the empties when it was broken open, and could then be reloaded much faster than a revolver with a side loading gate.
The main drawback to any Top Break revolver is that because the frame and barrel are two separate pieces, the frame can stretch over time from powerful loads, so eventually the latch may not be as secure as it originally was.
I can't tell you much about other company's revolvers with side swing cylinders, other than Colt first brought one out in 1889.
The first Smith and Wesson revolver with a side swinging cylinder was the 32 Hand Ejector 1st Model which was introduced in 1896. S&W called these Hand Ejectors because unlike the Top Breaks, which ejected their empties automatically, the side breaks could not employ the same sort of ejector mechanism. Instead the empties had to be ejected manually, or By Hand, by pushing back on the ejector rod.
Smith and Wesson followed the 32 caliber HE with the 38 Military & Police Model of 1899 in 1899. This was the first revolver chambered for the then brand new 38 Special cartridge and it set the pattern for all S&W double action revolvers that followed.