92FS, F, FS and G are all the same frame. They do not have a Picatinny rail which makes it a bit lighter.
Up until 2021, when Beretta released 92X with cutouts for red dot mounts, all 92's have no provisions for a red dot.
92 is has a unique recoil system. where the barrel does not drop the barrel to eject the spent cartridge. basically, the barrel never moves and stays level. this helps tremendously with recoil and the time it takes to get back on target.
96 is the same as 92 but in 40S&W caliber. It's literally the same gun with a different barrel.
92's handle is thick so people with average hand size(or smaller) have a hard time holding the gun and pulling the trigger in double-action mode. If cocked, the trigger is further back and pretty much any hand size can work the trigger.
Back in the day, Wilson Combat started modifying the handle by shaving the back where there was extra metal. this gave the handle(and the gun itself) a different look All new 92's such as INOX and X are now made with that shape at the factory. If you're looking for a classic Die Hard Beretta look, these new guns are not it.
92 A3 and A4, X, G(tactical version) have Picatinny rail for mounting lights.
The G series is just like FS. The Italian police, called Gendarmerie(thus the series name G), wanted a gun without a safety. the G series was born! It is pretty much the same gun except for the safety level which acts as a decocker only. 92 safety switch usually pivots the striking pin by 90 degrees to prevent any contact with the loaded chamber. It also decocks the hammer.
92 INOX is a stainless steel version of 92FS and is supposed to be the "Bling Beretta".
Shooting-wise, the gun feels nothing like a Glock or metal body CZ's, for example. It is VERY similar to 1911 in how it handles. One of the reasons Massad Ayoob and Bill Wilson, two of the biggest 1911 proponents, are also big supporters of Beretta.
The gun's history is "spotty" primarily because it was used in MASSIVE numbers by the US military. Two reasons people claim "it's bad!":
1) there was a single case early in 92's life with the military where the slide broke and hit a soldier in the face, almost taking his eye out. Beretta quickly changed how it manufactured the slide. There have been no reports of the slide ever breaking again
2) US military loves to get bottom-of-the-barrel quality stuff and push it on soldiers. This is EXACTLY what happened with Beretta magazines used by the Army. They gave the contract to the manufacturer who decided to modify the magazine to make it even cheaper to manufacture. This resulted in consistent feeding problems. The guns would jam pretty much on every magazine. It took the army 10 years to change the supplier! In those 10 years, the reputation of Beretta as a gun "with problems" has become a de facto reality. That said, if you can get your hands on a used army surplus Beretta and use a proper magazine, they will shoot perfectly fine without ANY feeding problems.
92's barrels do not wear out. It is not uncommon for a 92 with 30,000+ rounds through the barrels to shoot with exceptional precision.
92 recoil springs don't last beyond 10,000 rounds and need to be replaced.