OP, I say the best solution if you are gonna share your Watch is to create a new AppleID so that way there is no way you're calls and messages can ever sync together...fterall, you'll have both your phone and watch on you so you'll want peace of mind knowing it'll never be an issue. creating a new appleid for this purpose is the way.
Even is you could shut off notifications and syncing from the iPhone to the watch it would probably all reset come watchos10 and then watch0s11 and then watchos12..
Even is you could shut off notifications and syncing from the iPhone to the watch it would probably all reset come watchos10 and then watch0s11 and then watchos12..