This creamy sauce is just as flavorful as—but much healthier than—a traditional, mayonnaise-based tartar sauce.
Combine the yogurt with garlic, chili powder, 1/4 teaspoon pepper, and lime juice; cover and refrigerate.
Separate the squids' tentacles from their bodies (if that has not been done already); slice the bodies into 1/2-inch rings, and cut the tentacles in half if they're large. Rinse squid well, and drain.
Put the tortilla chips in a food processor; pulse a few times, then let food processor run until tortilla chips are finely ground. Transfer crumbs to a plate, and combine with remaining 1/2 teaspoon pepper.
Put 2 tablespoons of oil in a large nonstick skillet over medium-high heat. When the oil is hot, dredge squid lightly in the crumbs, tapping to remove excess; add to skillet without crowding. (You may have to work in batches, using remaining 1 tablespoon oil.) Cook, turning once, until the squid is firm, lightly browned, and opaque within (cut into a piece to check; about 3-4 minutes per batch). Drain on paper towels, and serve immediately with yogurt sauce, lemon wedges, and greens.