I also have been using Garmin HRM-Pro lately and there is some good data on what they call “running dynamics”:
https://www.garmin.com/en-US/garmin-technology/running-science/running-dynamics/
These are all Running Dynamics and its fields on the fit file (some of them already on intervals.icu):
Ground Contact Time (GCT): stance_time (ms)
Ground Contact Time Balance (GCT Balance): stance_time_balance (percent)
Cadence: cadence (rpm)
Stride Length: step_length (mm)
Vertical oscillation: vertical_oscillation (mm)
Vertical ratio: vertical_ratio (percent)
Running Power: power(watts)