After Updating to High Sierra, my bluetooth headphones have terrible sound quality Also, I can no longer pause and play using the button on the headphones. 

These are the Beats by Dre headphones that are included for students and educators. The quality is great when I plug in the wire connection.
Facing exactly the same problem, repairing/rebooting won't work.

But after I switched the mic setting back to Internal Microphone the standard audio quality is back. I guess the audio quality is degraded while the mic is active.