Can AirPods be used “seamlessly” between Mac and iOS devices?
I'm an AirPods user and so far I have not found them to switch seamlessly between my 2016 MacBook Pro and iPhone 7 Plus.

The switching is manual: select AirPods on the MacBook Pro, or connect Bluetooth on the iPhone. If a call comes through on the iPhone whilst on a Skype call on the MacBook Pro, you will have to pick up on the phone.

The "simultaneous" promise, so far, is marketing BS. Maybe it will work in a future software/firmware release.