In a 4-6 quart slow cooker, toss together the chicken, onion, garlic, chipotles, oregano, and 1 teaspoon salt. Cover and cook until the chicken is very tender, on low for 7-8 hours or on high for 3 1/2 to 4 hours.
Twenty minutes before serving, heat oven to 350 F. In a large bowl, toss the cabbage, radishes, and cilantro with the lime juice and 1/4 teaspoon salt. Wrap the tortillas in foil and bake until warm.
Transfer chicken to a medium bowl and shred, using 2 forks. Strain the cooking liquid through a fine-mesh sleeve into the bowl and toss with the chicken to coat.
Fill the warm tortillas with the beef and slaw. Serve with sour cream, pickled jalapeños, hot sauce, and lime wedges.