In a medium bowl, toss shrimp, taco seasoning, half of garlic, and ¾ tsp. salt until combined. Set aside until ready to use.
In a small bowl, whisk white scallion parts, sour cream, jalapeños, mayonnaise, zest from 1 lime, juice from ½ lime, ¼ tsp. salt, and remaining garlic until combined. If you desire a smooth sauce, blend in a blender or food processor until smooth, about 15 seconds. Set aside until ready to use.
In a large bowl, toss green cabbage, red cabbage, cilantro, green scallion parts, juice from ½ lime, and a heavy pinch of salt until combined.
In a large stainless steel or cast-iron skillet over medium-high heat, heat 1 Tsp. oil and swirl to coat pan. Once oil is shimmering, add shrimp in a single layer. Cook, turning halfway through, until cooked through and opaque, 2 to 3 minutes. Transfer shrimp to a clean medium bowl.
Reduce heat to medium, add juice from remaining 1 lime, and scrape up any browned bits from bottom of pan. Pour lime juice over shrimp. Wipe out skillet.
In same skillet over medium-high heat, heat 1 Tbsp. oil. Toast half of tortillas, turning frequently, until slightly charred on both sides, 3 to 4 minutes. Repeat with remaining 1 Tbsp. oil and tortillas.
Divide shrimp mixture and coleslaw among tortillas; drizzle with crema. Top tacos with avocado, radish, and more cilantro.
