Beta release (now a full release) helped for point 1.
Regarding point 2, there is two kinds of energy tweaks in the Samsung settings.
One is Settings → Device Care → Battery - > App power management → Apps that won’t be put to sleep. I added Yatse here, but it did not help with point 2.
The second one is to go to app info (long press on app icon) → Battery → Optimise battery usage → disable. This seems to control the wake locks you mentioned and actually seemed to help with point 2. An app for which battery optimisation has been disabled cannot even be put into the list of “apps that won’t be put to sleep” (probably because all energy management options have been turned off for this app).
Thanks for pointing me the right way here!