RE: Best engine for Twist V2?
Since you have not yet bought the airframe, I'd suggest a Valuehobby Sabre ARF or Swanyshouse MoJo or Primo kit.
They are MUCH better at 3D and the engine I would choose for them is a 55AX with a 13x4 APC sport or Xoar or a YS70 with a 13x6.
Either of those will rock a 40 size 3D bird.