The Size of your Screen will not effect your FPS.... I rephrase "Should Not" in most cases if your machine is running smooth now..Go Big as you can.... you will love it:ehh:
the only thing you have to worry about with running form your computer to tv is the refresh rate. Nowadays, 120hz is ideal. I run on a dell xps 17 that has a 60hz refresh rate and run hdmi to the tv which is 60hz.