Go checkout intervals.icu to track your pmc. Just sync your trainerroad calender then you are in total control over youre training and finess.
My experience with Garmin’s VO2Max estimates are limited to (a lot of) FR230 running data/workouts, for a number of years, during which I also did a few beep tests - and the Garmin/FirstBeat algorithms constantly over-estimate my VO2Max, particularly when I get into serious running training - as in 51 ml/kg/min vs 44. The beep test results are well correlated with my 10k performance. The running performance predictions from FirstBeat get into delirious areas - I’d love them to be true…