I have the same problem as Janerat - ever since upgrading to iOS 14, phone calls have been too loud with airpods, even at the minimum volume setting. Neither of the two articles above was helpful. "Headphones Accommodations" doesn't provide a way to reduce volume, only to boost it or adjust dynamic range boosting.
To be more specific, the problem is likely occurring when the airpods enter the bluetooth HFP profile usually because an app has switched audio categories to playAndRecord. In A2DP for audio playback, the airpods volume can be set to zero, but in HFP, the minimum volume level still produces audible output. That lowest level seems to have changed between iOS 13 and 14, and is now perceived as too loud by some people.
You guys likely have a good reason for disallowing ~functional~ muting in HFP - perhaps so that it's less likely I'll have a hot mic without being able to hear people respond to me (therefore making me aware I can be heard). Whatever the reason, it's pretty much ruining the iphone/airpods experience for me. I use the phone app and a variety of other VOIP apps day in and day out, and in my quiet office, nearly everyone is too loud. I've now had to switch to wired headphones for most of that activity, which is pretty lame.
Please consider reducing the minimum amplification setting for airpods in HFP for everyone, or adding a setting to reduce it personally.