This is a very old thread, but the asker makes a great point: This is not documented well anywhere I can find. There is a description of when to use each setting, but not what each setting does in detail. Is there a more detailed behavior guide for each of these settings somewhere?
Based on different EDCA profiles, different class of traffic (Voice, Video, Best Effort & Background) get different transmit opportunities. Below slide that explain TXOP is from above cisco live presentation.
If you go through below twitter thread, you see Mark compare these EDCA parameters when you set WMM, Voice Optimized & Fastlane. (Cisco slide shows TXOP in Fastlane profile)