How do I switch Apple Watch's "Now Playing" source between "phone mode" and "watch mode"

The Apple Watch "now playing" control allows me to quickly adjust volume from my wrist without pulling out my phone. Once I purchased AirPods and connected them to my watch, my entire user experience changed: I discovered that music can be played "from" the watch, or "from" the phone. The problem is that I don't see a consistent way to bring up the device chooser (AirPods or iPhone) when 1. Music is playing/streaming from one device and not the other 2. Music isn't playing anywhere 3. Music or Audio is playing on both devices (strange ...but seemingly default use case) 3. Non-iTunes audio (as in Audiobooks or Safari) on the phone I'm having a difficult time with this UX and any navigational tips would be appreciated