Choppy sound is an indication the hardware can’t keep up with the emulator.

Have you run sudo raspi-config and set overclock to Pi2 setting?

Also in raspi-config, try giving the video more memory (the 1gb on the Pi2 is shared between system and video). Try 256, 384 or even 512 video and see if that helps.

Other than that, you’ll have to wait and hope for better optimized versions of RetroPie that improve performance.