Add chicken pieces, water and Buffalo sauce to the pot and stir to coat. Sprinkle ranch dip over the top, then dot with butter--do not stir. Secure the lid, making sure the vent is closed. Using the display panel select the MANUAL or PRESSURE COOK function*. Use the +/- keys and program the Instant Pot for 15 minutes. When the time is up, quick-release the remaining pressure. Carefully remove the chicken from the pot to a cutting board and shred thoroughly (a hand mixer works great for this job). Return chicken to pot along with softened cream cheese and shredded cheeses. Stir until well blended, returning to SAUTE mode as needed. Serve hot garnished with a swirl of additional hot sauce alongside chips, sliced baguette or veggies.