Using a vegetable spiralizer, spiralize sweet potatoes and beets (no need to remove skin). Place on a greased baking sheet and toss with oil and ¼ teaspoon salt. Bake 25-35 minutes, until very crispy, tossing with tongs occasionally. Sprinkle with additional salt, if necessary.
In the meantime, coat a baking sheet fitted with a wire rack with cooking spray. Set aside.
Sprinkle fish filets with salt and black pepper. Set up three bowls: One with the flour and a pinch of salt, black pepper and cayenne; one with beaten egg and a pinch of salt and pepper; and another with panko, and a pinch of salt and black pepper. Coat fish filets with flour, then egg wash, then panko, and place on the greased baking rack. Coat each filet with cooking spray. Bake 10-12 minutes, flipping once and coating with additional cooking spray, until outside is crispy and interior temperature reaches 145 degrees.
While fish and curly fries bake, prepare tartar sauce by whisking all sauce ingredients in a small bowl. Taste and adjust seasoning, if necessary.
Serve fish with tartar sauce and a side of crispy curly fries.