Brush both sides of the tortillas with 2 tablespoons of the oil. Heat a large skillet over medium-high. Working in batches, sear the tortillas until they’re lightly browned and starting to crisp, for about 1 minute per side. Set the tortillas aside until you're ready to assemble the dish.
In a medium saucepan, bring the chicken broth, chiles guajillos, garlic, salt, oregano, and pepper to a boil. Remove from the heat, cover, and let sit until the chiles are soft, for 30 minutes. Transfer to a blender and puree until smooth.
In a large heavy pot over medium-high, heat 2 tablespoons of the oil. Cook the chicken thighs until deep golden brown, for 5 to 6 minutes. Turn the pieces over and brown the other side, for 5 to 6 minutes more. Transfer the chicken to a plate. If there isn’t at least 1 tablespoon of fat in the pot, add the remaining 1 tablespoon oil along with the potatoes, carrots, and onion. Cook, tossing occasionally, until the vegetables are lightly browned, for 4 to 6 minutes.
Pour the chile puree into the pot with the vegetables; scrape up any browned bits from the bottom of the pot. Nestle the chicken into the sauce and bring the mixture to a boil. Cover the pot, reduce the heat to low, and simmer until the chicken is completely tender and cooked through, for about 30 minutes.
Stir the vinegar into the pot and mound the chicken and vegetables on one side so there’s room on the other side to dip the tortillas into the sauce.
Using tongs and working with one tortilla at a time, dip into the chile sauce, turning to coat, and cook in the sauce until softened, for about 3 seconds per side. Transfer the tortillas to a baking sheet as you go. Spoon 2 tablespoons of the queso fresco across the center of each tortilla and fold over like a taco.
Divide the enchiladas among four plates and spoon more chile sauce over top. Top with lettuce, pickled onion, sour cream, cilantro and any remaining queso. Serve with the chicken, vegetables, remaining sauce, and pickled jalapeños.