In a large bowl, whisk together the avocado oil, coconut aminos, lime juice, garlic, chili powder, salt, pepper, and cumin. Add the portobello mushroom caps and poblano peppers and toss until well coated. Set aside to marinate at room temperature for 15 to 30 minutes.
Preheat the grill over medium-high heat (about 400°F). Dip a wadded paper towel in the avocado oil and, using tongs, wipe the oil evenly over the grates. Be careful not to use too much oil to avoid starting a flare-up—a little goes a long way here.
Place the mushrooms and peppers on the grill, close, and cook until browned and tender, 4 to 5 minutes per side. Transfer to a cutting board and slice.
Warm the tortillas on the grill, about 2 minutes per side, leaving the cover open.
Serve the sliced mushrooms and poblanos in the warm tortillas with guacamole, pico, cilantro, and hot sauce, if desired!