Joe is big, friendly, and curious. He's also unclean, and not very swift on the uptake. Or at least, that's how he appears on the surface. He's actually a real bastard that killed Dogbody's dogs, and might have raped someone (unproven). He has black hair, a fat face, and overalls. Joe doesn't care about leaving Denver, he's just in it for the loot. He is friends with Bean, for the liquor, and Hardin, for the big loot.
If the Prisoner is female and sleeps in the Salvager camp, in the middle of the night she is awakened by Slow Joe. He will say "I think I want to fuck you," and if they let him, then that's that. If she doesn't let him, he says, "I'm going to fuck you whether you say you want it or not, bitch!" and initiates combat by slapping the her. However, this won't happen if Porter assigns Jimmy T as the Prisoner's bodyguard (done via dialogue with Porter, and Jimmy will be present when Slow Joe arrives which will deter him).
Not dealing with the traitor Salvagers before attempting to explore the Box will, in a cut scene, result in a violent conflict as the traitors turn up looking to take it for themselves. If Bombay Jack also wasn't dealt with it will include him detonating the bombs in his base in an attempt to take everyone else out with him. The Prisoner and any companions will be scattered around the rubble alive but severely injured.
If the Prisoner puts off exploring the Box for long enough, the traitor Salvagers will go ahead with their plan to strike it. The Prisoner will hear their interactions over a radio and may be able to get their before the showdown if he is quick. If not, he will reach the Box only to find that Jack was able to snipe or bomb all of them and will already be stripping their corpses, he will already have done this too if the Prisoner puts off investigation even longer.