Preheat the oven to broil. Preheat a deep-fryer or heavy-bottomed pot, with enough canola oil to come halfway up the sides of the pot, to 325 degrees F.
Working in batches, deep-fry the sweet potatoes until crisp, about 5 to 7 minutes. Remove from fryer to a paper towel lined platter and season with salt and pepper, to taste. Set aside.
Add the grapeseed oil to a large saute pan over medium-high heat. Add meat and brown it until almost cooked through, about for 3 to 4 minutes. Add the onion and garlic and cook until softened, about 2 to 3 minutes. Add the tomato paste, chipotles, and salt and pepper, to taste. Stir several times to incorporate. Add the BBQ sauce, bring to a simmer and cook for an additional 5 to 6 minutes. Remove from the heat.
To assemble nachos:
Using 2 oven-proof platters, lay some sweet potato chips on each platter. Top the potatoes with some meat, cheese, and jalapenos. Repeat the layers with the remaining ingredients, except for a handful of jalapenos. Broil until the cheese melts, about 3 to 4 minutes. Remove the platters from the broiler and top them with the remaining jalapenos, a drizzle of BBQ sauce and the scallions. Serve.