airpodsbluetoothiphone
I own AirPods and connect to by my iMac (for video conference) and iPhone (for phone calls).
How do I get the AirPods to switch to the device that I want to use?
I can't turn bluetooth off on the iMac because then the mouse stops working. If I select AirPods on the iPhone when I am on a call nothing happens. But if I restart the computer then I can use it on the iPhone while the computer is not on bluetooth.
Apple assumes that wherever you answer from is where you want to hear the audio.
The fact that your AirPods are unresponsive to your taps is a separate issue (maybe Apple will address in future updates). The expected behavior is that if you want to answer on your AirPods, you'll tap on them.
Apple has always these kind of bugs with their wireless (or even wired) platforms. You just need to force it to connect.
So you can go to sound settings of system preferences and force connect there.
or if you already have the indicator in the status bar 
, you can option+click on that and force connect from there.
Note that it could either fail because it may be in-use or disconnect from the other source that already connected and using it (Randomly but second option most of the times depends on what device requested new connection and what device is using it right now).
It always helps me and hope it helps you as well.
Best Answer
Under the Listen with your AirPods section of this Apple support document: