@acceleration
So, what you would need to do with your metaplot would be to enforce some rationale as to why the characters would be against each other. The thematic aspect of the meta could literally be anything, from vampires and whatnot fighting hunters (like @ThatOneDude mentioned), or something like what we did on TR the first couple years when I was running it and have it stem from some kind of eldritch horror thing. Nonetheless, the meta needs to establish the animosity between PCs.
My suggestion would be similar to what was said before: have a few tiered Conspiracies in the area - pick three of them that don't work well together, like Task Force Valkyrie, the Cheiron Group, and the Ascended Ones, for example - and put them in a location that's highly anomalous. Your metaplot could be something as such: after a massive war between some extra-spatial beings (spirits and the like) and supernatural creatures in the mortal world, a section of the Amazon Rainforest has been cordoned off by the United Nations. Three groups of supernatural Hunters, one even funded by the United States government, have come forward to deal with the potential threat. Everyone knows about the existence of the supernatural now, as the Shadow now bleeds into the real world in the location where the last great battle was fought. Hunter cells are expected to travel into the Bleed Zone (B-Z) to take care of any obvious threat to the surrounding population, and most of the people in the area have been evacuated to safer locations. Each hunter conspiracy has its own reasons for being there, down to specific cells. Your orders from on high are to acquire any anomalous artifacts and equipment from the B-Z and bring them back to base camp in order to be studied and figured out to ensure that something like this never happens again. With luck and enough research and development, humanity may even be able to close the rift between the Shadow and Earth.
In this sort of setting, you could have supernaturals rounded up and captured, or in deep, deep hiding. They wouldn't be PCs, but you could throw just about any sort of PvE antagonist into the mix by using the stats from one of the splats. Vampires who have Blood Tenebrous interested in the Bleed Zone? There you go, now your Cell has to fight a Coterie of OD. Werewolf pack moves in while a TFV cell has an Ascended Ones cell pinned down with machine gun fire, and now the two groups have to fight off the werewolves. Then the one that takes the least casualties fighting off the theriomorphs finds that their former opponent is much less equipped to deal with them, so they take 'em out. The Cells are being run like a military op, with each other Conspiracy acting as a different military group, and therefore enemy combatants.
So PrPs could be something like: we're going into the B-Z to find this powerful fetish that was used in the big conflict. Word gets out to the other Conspiracies that this thing exists and they send in some of their own soldiers. Who can get to it first, and who can hold off long enough to get extracted? Or... We've recovered this artifact from the B-Z and now our best scientists are working on it back at base camp. But it seems like one of the other Conspiracies realized that we've got it, so now we have to defend our scientists from an all-out assault and push the enemy back. Even something like: we've figured out the properties of this vampire blood magic anomalous entity and we're about to have it extracted back to Washington D.C. so we can put it to use as best we can in defending humanity from the depredations of our supernatural enemies. Unfortunately, the Cheiron Group wants to take credit for its discovery and potential defensive abilities, etc., etc., etc.
Forgot to write out: So, the PrPs would push both the meta and they'd also theme themselves toward PvP, just by the nature of what sort of military operations are done into the Bleed Zone (or whatever you wanna call it).
Stardew Valley
