Just as an FYI, the Garmin running power and the Stryd running power run in parallel. The Garmin power data does not replace or override stryd in any way, and vice versa. If you use both an HRM-Pro and a Stryd (as I do, too), then you will end up with two power data charts in the activity on Connect, but that's fine really, just ignore the Garmin data if you want.
Likewise, on the watch you can just use the Stryd datafield instead of the native Power datafield, if you want.
Or as Nickk recommended, if you don't care about any of the Garmin running dynamics data then you can connect the sensor as BLE, which will disable that since the HRM-Pro can't do RD data over BLE.
