As we don't really know the story itself, it's impossible to say who the main characters are.
Given that we have no details about 'lamerican horror story', we can just hypothesize. There might be a character who is a bit of an outcast, someone who doesn't fit the typical American horror hero mold. They could be nerdy or just really unlucky, and they end up in the middle of some spooky events. It could also have a villain that is not the typical menacing figure but rather something more unexpected, like a cute - looking but actually very dangerous creature.
Since we don't have a clear definition of 'lamerican horror story', it could be a horror story that is set in America but has a really different take on the genre. For example, instead of the usual haunted houses or serial killers, it could focus on something more mundane like a malfunctioning toaster that starts causing spooky events. It could also be about a group of really clumsy or incompetent characters who are trying to survive in a horror - like situation.
It might be a lone traveler who stumbles upon the well during his journey. He has no idea of the danger that lurks within it. There could also be an old hermit who lives near the well and knows some of its secrets, and he might be involved as one of the main characters, either trying to protect others from the well's horror or being part of the source of the horror himself.
Often, there's a protagonist who is new to a place, like a person who just moved into a supposedly haunted house. This character then has to face the manifestations of the ghost. There may also be a local character who warns the protagonist about the ghost but is ignored at first.
In the 'Dunwich Horror Story', there might be a local investigator or a curious outsider as main characters. They are the ones who get drawn into the strange happenings in Dunwich. There could also be some local townsfolk who play important roles, either as victims or as those who know some secrets about the horror that plagues the town.
There's the radio DJ. He's an important character as he narrates the different horror stories throughout the movie.
In the 'Goldilocks horror story', Goldilocks is the central figure who unknowingly steps into a world of horror. The three bears, instead of being simple woodland creatures, could be transformed into something far more terrifying. For example, they might be werebears with a taste for human flesh. Additionally, there could be a dark spirit that haunts the house, making it a character of sorts. This spirit could be the one luring Goldilocks into the trap, adding another layer of horror to the story.
I'm not sure specifically as I haven't read or watched it in detail. But it could be a group of young people who find themselves in a terrifying situation in Texas. Maybe they are travelers passing through and stumble upon the horror.
There are several main characters as it's an anthology. There's Santa Claus in his darker incarnation, some students who get into trouble in one of the storylines, and a family that faces horror in another.
I'm not sure exactly as I don't have detailed knowledge of this particular 'Dhootha horror story'. But usually in horror stories, there is often a protagonist who has to face the horror, maybe a young person who is brave or naive at the start.
There might be a villain who uses magic for evil purposes. Maybe a witch or a warlock. And there could also be a group of innocent bystanders who get caught up in the horror caused by the magic. Without reading the actual story, it's hard to be certain, but these are common character types in magic - horror stories.