Line a 13x9 inch baking pan with parchment paper and spray paper with cooking spray
Melt butter over medium-low heat. Add marshmallows and marshmallow creme; cook and stir until melted, about 5 minutes
Remove from heat; stir in vanilla and salt
Add rice cereal, cornflakes, pretzels, and 1 1/2 cups strawberries to marshmallow mixture and stir to combine
Press mixture firmly into your pan using a either a spatula or a piece of parchment paper sprayed with cooking spray; gently press remaining strawberries and pretzels into surface of bars
Let stand at least 4 hours before cutting. Using parchment, lift uncut bars from pan and cut into bars