Bought a pair of QuietComfort 35. Audio quality on MacOS was lagging compared to iOS. Googling led to different posts suggesting the use of Bluetooth Explorer to force aptX usage. Did the trick for me.
Bluetooth Explorer can be downloaded from https://developer.apple.com/download/more. Search for Hardware IO tools:
Open Hardware_IO_Tools_for_Xcode_7.3.dmg and launch Bluetooth Explorer:
Select Audio Options:
Check Force use of aptX:
Don't forget to disconnect and reconnect your Bluetooth device.