Bluetooth headphones (such as AirPods) generally have a range of 30-60 feet (10 to 20 meters) depending on conditions, walls, interference, etc…
But Bluetooth headphones to the iPhone have nothing to do with the Apple Watch.
That is to say
- Bluetooth headphones paired to iPhone is 30-60 feet
- Bluetooth headphones paired to Apple Watch is 30-60 feet
- Apple Watch Bluetooth paired to iPhone is 30-60 feet.
If the Apple Watch and iPhone are too far apart for Bluetooth (the preferred low lower connection method), but still in your home, then they can talk via your home WiFi network.
But once your Apple Watch and iPhone are out of WiFi range and your iPhone, then the GPS only Apple Watch is no longer able to access the internet via your iPhone not WiFi, and can just record your exercise session, tell time and date, and if you have transferred music or podcasts & stored them on the Apple Watch, you can listen to that previously stored audio via Bluetooth headphones paired to to your Apple Watch.
NOTE: I do NOT know if any music streaming services allow you to store your playlist music offline on an Apple Watch. You would have to check with your service. Personally, I’m old school (because im old 😀) and all my music came on CD’s, that I copied to my Mac, then to my iPhone, and from there I was able to physically copy the music to my Apple Watch. It works when my iPhone is not nearby.
NOT: I’ve been using a GPS only Apple Watch for 6 years, because my iPhone is basically glued to my body, so it is never far away.