3. See all activities in Garmin Connect. She uses a Garmin Edge 530 computer for cycling. The HRM sensor connects easily. For running, it is not possible to use just her iPhone with the Garmin Connect app. She also uses an Apple Watch, and she is not willing to use/buy a Garmin Smartwatch.
Running power zones can be configured to be based on LTHR (I think it's actually the default), so if LTHR updates as above, your running zones will automatically follow. With the Stryd, I pretty much had to do all out 5k or 10k TT's to get an updated CP, so Garmin's system is a bit smoother, but it may take a bit longer to get to the true LTHR
Garmin HRM-Pro Premium Chest Strap Heart Rate Monitor. $135 at Amazon. $135 at Amazon. You can connect it to your phone or smartwatch, in addition to exercise equipment like treadmills and
The new Garmin Forerunner 255S is a superb multisport watch. It's an excellent update to the Garmin Forerunner 245, not just because of the addition of the new sensors. It's the smallest mMTB.