Slow VSE

So, I have been working on a video in the video sequence editor for about 2 weeks now. It’s 1920x1080 at 60fps with about 20 video strips input. The thing understandable is slow when I press play. The video is finalized but I want to add audio. How can I listen to the audio/video in real time. Do I need to render out the video and import it back in? Should I use another audio program to fade mix sound clips? The audo is primarily commentaries with a crowd background so it doesn’t have to be precisely in sync.

VSE > Shift A > Sound (Select Audio file) > add sound strip
Time line > Playback > AV-sync

Render
Properties > Render > Dimensions, Output and EnCoding Settings (don’t forget to choose the audio codec)
VSE > OpenGL Render or Render > Animation