Position racks in the upper and lower thirds of the oven, and preheat it to 425°F. Line two baking sheets with parchment paper and set aside.
Place the sweet potatoes, avocado oil, cornstarch, if using, smoked paprika, garlic powder, and onion powder in a bowl. Toss well to combine. Divide the sweet potatoes between the prepared baking sheets and spread them into a single layer.
Bake on the upper and lower oven racks for 15 minutes. Flip the fries, rotate the baking sheets, and switch the positions of the baking sheets. Bake for 10 to 15 more minutes, or until the fries are brown and crispy on the edges.
Meanwhile, make the aioli: In a small bowl, combine the mayonnaise, lime zest, lime juice, garlic, chipotle powder, and smoked paprika; stir well to combine. Add fine salt to taste.
When the sweet potato fries are done, sprinkle them with fine or flaky salt, pepper, and/or chopped fresh parsley, if desired, and serve right away with the aioli.
Store leftovers in separate airtight containers in the refrigerator for up to 3 days.