I'm not the first one to suggest that the Vigilante's dual identity stuff feels like it should be a series of feats or something instead of a class feature, but I feel like the status quo makes the Vigilante's dual identity feature pretty worthless on an NPC, assuming that you have mechanics-savvy players. Basically, as soon as an NPC Vigilante does something mechanically that makes it clear that they're a member of the Vigilante class (or likely a member of the Vigilante class), the gig is up, assuming that your players recognize it. The players can avoid metagaming by having their characters act like they don't know, but the surprise is still spoiled for the players, and I feel like avoiding acting on knowledge when it comes to major plot things is kind of unsatisfying (and pretty much impossible to do perfectly).
Alternately, the DM can carefully have the NPC dance around doing anything that suggests they might be a Vigilante, but for most specializations that means ignoring a lot of what's cool about the class.
In this regard, I feel like the Vigilante is fundamentally misconceived as a class, at least in terms of being an antagonistic NPC. As soon as the players can tell that the bad guy is a vigilante, it tells them that someone else - probably someone else they know or will meet (otherwise why have the character be a vigilante?) - is the same character, and given what the social identity is capable of, that usually narrows down the options considerably. That's a potentially huge campaign spoiler given away by the nature of the class design.
If the Dual Identity features were instead a feat chain, that would solve this almost entirely. The NPC antagonist wouldn't have to avoid using class features in order to avoid giving away that they have a dual identity, because they have the same class features as their base class. They'd be down a feat or two, but "this NPC has a few feats unaccounted for" is virtually impossible for the players to detect.
Ironically, this makes the Vigilante perhaps the single worst class in the game for an NPC that's supposed to have two identities, assuming you have reasonably mechanically savvy players, because it's the only class that tells the players "I have two identities." If you want to have a two-identities NPC antagonist, you're much better off making them literally any other class and then using PF's pretty extensive array of identity-shielding items and mechanics to paper over the differences.
I haven't been following the playtest super closely, so maybe this a known issue with a good solution already proposed, but as it is it seems like it's a pretty serious flaw.
I very much like the Vigilante talents, and I think the four-subclasses structure is fine, but having the other class features be huge tells regarding Dual Identity mostly spoils the class as a class for NPC baddies.