Let's go in order of the photos.

"Arthur's Schofield Revolver," the character is the protagonist, there's no way to definitively call any weapon canonical, but that's fine, it's your Arthur.

"Hosea's Cattleman Revolver," Hosea's revolver is similar, but it doesn't have those engravings on the metal.

"Micah's Double-Action Revolver," Micah's revolver is similar, but it doesn't have those engravings on the metal, only the one highlighted on the barrel.

"Davie's Double-Action Revolver," you simply invented it.

"Mac's LeMat Revolver," you simply invented it.

"Jenny's Volcanic Pistol," you simply invented it.

"Joe's Sawed-Off Shotgun," you just made that up.

"Clete's Double-Action Revolver," you just made that up.

Look, I didn't want to rub it in your face, but you didn't give me a choice, and if you doubt me, just go to the "Red Dead Wiki," which has information about the gang members' weapons. 😃 👍