Season chicken with cumin, chili powder, salt, and pepper.
Set Instant Pot to SAUTE and add olive oil. Sear chicken on both sides, then remove and set aside.
Turn off Instant Pot, add water, and deglaze the pot. Return chicken to the pot and add 1/2 cup enchilada sauce.
Lock lid, cook on high pressure for 8 minutes, then quick release. Check chicken for doneness, then remove and shred.
Reduce sauce in Instant Pot by simmering for about 5 minutes.
Preheat oven to 350 degrees F. Warm tortillas in the oven until pliable.
Mix shredded chicken with reduced sauce, half the green onions, Greek yogurt, and 3/4 cup cheese.
Spread 1/2 cup enchilada sauce in a baking dish. Fill tortillas with chicken mixture, roll, and place seam-side down in the dish.
Top with remaining enchilada sauce and cheese. Bake until cheese is melted, about 15 minutes.
Garnish with remaining green onions and optional toppings.