That should be much easier to optimize against vs having no paging at all though. Are Apps running in the background asked to free up storage or be killed before the active app needs to do the same or are they referring to the active app ?

Background apps are even worse, as by default they are suspended.

If the system requires memory the ones with higher memory footprint are the first ones to go. They aren't asked nicely, just killed.

This might have changed on newer versions though. I am typing this from memory.

Also on the Watch there are also time constraints. How quick an app is allowed to execute.

Windows Phone also has similar constraints.