RE: What Size Evo?
For true high performance wave sailing, no doubt the EVO 62 would be the right choice at your weight. However, when you don't have that much wave experience, I think the EVO 70 will indeed be a better board. It will be more forgiving and probably make you progress faster in the waves. I think the extra size will also make it crossover into freestyle a bit better too. The EVO 70 is also very controllable and extra versatile when it comes to differerent types of wave conditions. It will also give you a healthy overlap with a Freesex 86 or Flare 88.
So, EVO 70 is my recommendation. I weight 68 myself and its my favourite board.