I got the Grey Performer bundle with the HRM-RUN heart rate monitor. It's definitely getting the bundle as the HRM-RUN enables a whole load more functionality. VO2 Max estimation and advanced run dynamics etc.
The severe battery drain is usually caused when the BT connection gets disrupted for whatever reason and the watch is constantly trying to reconnect. Sometimes disabling BT and re-enabling it on the watch and or phone will sort the connection out, sometimes not.
It doesn't seem to be a range problem, I've suffered with the watch and phone less than a meter apart when the connection has gone. This makes me inclined to believe it might be as much a problem with the BT stack used by Garmin Connect Mobile as the watch itself.
This has come and gone over the software versions from around V5 but the last couple of beta versions (6.82 and 6.84) have behaved themselves very well for me.
As a related tip, I find that if I am running or biking without my phone, disabling BT lessens the impact on battery drain during the activity.