Add stock, butter, garlic powder, hot sauce, pepper, and salt to Instant Pot. Stir. Add macaroni to pot and using a wooden spoon, push noodles into the stock making sure all are covered.
Secure lid on Instant Pot with pressure valve closed. Select PRESSURE COOK/MANUAL, and set the timer for 4 minutes. Once the timer goes off, "quick release" pressure by turning the vent to VENTING.
Carefully remove the lid from the pot. Add ¼ cup of Half and Half along with ½ of grated cheeses. Stir to combine. Add remaining cheese and add more Half and Half if needed. Stir until all cheese is melted. Taste and adjust seasoning. Serve immediately.