Same problem here with my airpods 2 and my MBP 16 with big sur. The sound quality is really poor. No sound quality problems when it's connected to my iphone EDIT : I have reset my airpods and everything works fine now ! https://developer.apple.com/forums/thread/662645?answerId=650400022#650400022

Thanks jaksen93, everything works fine now. The sound quality is better now Don't forget to change the balance and put it on the middle if only one airpod works

My problem is came back. When I check in "Audio MIDI Setup" app, the output bitrate of my airpods was stuck to 1 channel 16kHz. I have to switch my airpods from my macbook pro to my iphone and finally to my mbp to have 2 formats : 1 channel at 16kHz 2 channels 48kHz The second one has resolve my issue I don't know where the issue comes from but it's really weird