How to beat weaker opponents? What opening?

Hello, I would like to receive some information on beating weaker players. My rating is around 1200, and I tend to "play to my opponents", as in if I play a 900 player I play around 1000 and if I play a 1600 player I play around 1450. Is there any way I can play better against weaker opponents. I mostly am asking this to find the best oppening for weaker players. I have heard that the higher rated player usually wins the Ruy Lopez, is this accurate? Any opening best for playing people who are worse than me would help. Thanks!