Pour vegetable oil into a large heavy skillet, using enough to cover the bottom with 1/2-1 inch of oil. Heat to 350 degrees.
Meanwhile, slice your fish into 1/2 inch wide strips, 5 inches long. In a medium-size mixing bowl, make your batter by whisking together flour, baking powder, mustard, garlic powder, onion powder, salt, pepper, and root beer. Set aside.
Make your avocado salsa by combining diced tomatoes, onion, cilantro, avocados, lime juice, and salt in a bowl. Toss together to combine.
Make your simple slaw by tossing together shredded cabbage with red wine vinegar. Season generously with salt and pepper, to taste.
Working in batches, dip fish into the prepared batter to coat. Place directly into the 350 degree oil. Fry until deep, golden brown, about 3 to 4 minutes per side. Let drain on a paper-towel lined plate.
Serve fried fish hot on a corn tortilla. Top with slaw, avocado salsa, and jalapeno crema.