Moreover, to your attention: the default Garmin's stock face redraws the screen every second as well, even when idle (!!), it redraws the seconds hand, updates the steps, heart rate, weather, etc. More rich images or busy watchfaces will apparently lit more AMOLED pixels, hence in OLED every individual lit pixel consumes energy but black ones. Garmin's VA/Venu AMOLED-display has a more noticeable battery impact depending on the depicted image and watchface. You dived deep into the subject of the screen technologies, but in the specific case discussed it has no impact at all, Vivoactive has MIP-display for every watchface. Others like Samsung, AW only last à couple of days too so, VA/Venu are on the same level with those. Watches like tic watch use a secondary screen for always on to make battery last longer but that screen it's also not fancy. Now, problem with using something like actiface / gearmin on VA/Venu is that those screens (LCD/OLED) use power do display a pixel, so, a busy watchface will draw even more power to render it all. There are some good ones like alfa Zulu, fusion, etc which have a DND mode so, overnight they turn off most of the data fields saving power.
#DEVELOP GARMIN WATCH FACES UPDATE#
That means Bluetooth connection + a large payload on every weather update so, when possible set the refresh to 20min/half hour for weather.
Until the last CIQ, devs had to use and will use 3rd party service for weathe on older CIQ devices. This means fields like seconds, HR, charts, etc that do updates often, draw more power. The screen on most of Garmin watches (memory in pixel) use power when a pixel changes status not when it's "on".