The existence of the Wild West might be remarkable, but it's something that happened to and among other people.
Deciding to move to the Wild West isn't something that "happens to you". Proactive, not reactive
So clearly it cannot be A or B.
What brings the game to the wild west? Did it start there? Did the players decide to go there? Did the GM decide to bring them there? When they get there, do they have an agenda? Do they just wander around and experience random events?
B is both continual and related, and D is neither of those things. It can't be B.
That's my fault, I had mixed up my A and B. I've edited my last post.
I view it as A. I think it's A because the things happening are unrelated to the characters goals or themes.
But no remarkable events are "happening to" them, so it cannot be A. And even if it were A, that would disprove your argument about A being no more realistic than B!
Again, my fault for mixing up my own points! I view this as B.
If I'm a Roman citizen in 100 A.D. and I go to Rome and try to kill the Emperor, interesting things are going to happen to me, but my probable crucifixion and death is not improbable or unrealistic! I can't give a modern example due to ENWorld rules (even the Roman example risks Umbran's wrath IME) but hopefully you get the gist. Making interesting things happen around you by doing interesting things does not require becoming a Weirdness Magnet the way B does.
Your words: "If they aren't proactive, then things are still going to happen to them because it's a game and we all want stuff to happen. Wherever they go, they run into significant events, unrelated to their own agenda."
If you're making the interesting things happen, then I think it would be a case of my B. The weirdness magnet angle is more A, where remarkable events keep happening around the characters that are unrelated to them.
But here's the thing. Even a "random encounter" can be made dramatically relevant to the players' characters. So you roll brigands on your random encounter table, and we know that the Knight character has a Drive of "Justice". The PCs are on their way to the kingdom to prevent a major threat, but this random encounter occurs. They can avoid it and be on their way for their important goal... but does the Knight's sense of Justice supersede that goal? What does his decision say about him as a character?
That's dramatically relevant.
I think this idea that everything needs to be specifically connected to the PCs at all times is misleading. There's no reason even random encounters can't be made to be dramatically meaningful to one or more PCs.
Can you see how much your argument relies upon the false dichotomy that excludes C, D, and E from existing? You even said it yourself: "If [not E], then... [unrealistic things will happen]." You're implicitly acknowledging that E (no improbable events occurring except through player instigation) is more realistic than B (improbable coincidences related to player character's interests and themes, i.e. becoming a Personalized Weirdness Magnet).
A/B is a false dichotomy and should not be used to unilaterally dismiss realism as a genuine concern that some people have. If you do, you will never understand why people have that concern. You'll be talking to yourself about a riddle in a language you've forbidden yourself to learn.
I think your C, D, and E can all be categorized under A or B, so I don't think I'm excluding anything. My point is that A and B are equally realistic (or equally unrealistic, depending on how you want to look at it), so any distinction between the two is simply a matter of preference. So using it as a measure of play doesn't really seem too meaningful.
You could point at my game and say "wow, everything seems to revolve around the players' characters, that seems a bit too coincidental, no?" and I could point at your game and say "wow, nothing that happens to the players' characters has anything to do with them, that doesn't seem believable". Neither is right or wrong. And I also expect neither of our games would totally exclude A or B.
So instead, let's look at what's happening outside of the fiction. What's happening in the game, at the table. Drop all appeals to realism, and tell me from a process standpoint, what's the difference between A and B?