i have tried the double tap gesture that can be set up through the Accessibility settings.
i have the Series 8, running WatchOS 10.0.1)
i only spent about 10 minutes with it, but couldn't get it to get work reliably.
and, the actual gesture that was needed in order to get it to work required a very determined (exaggerated) kind of double tap that was tiring.
i think if i spent more time with it i could have gotten better at it.
for the above reasons, and, given the learning curve required to understand what double tap would do for each app at a given time, made me give it up.
but it made me think that the marketing claims by apple that the Series 9 is faster (processor speed) is probably correct.