Everything is subjective, but I personally turn off all of those continuity features. I have nothing to hide, but I share 3 mac's, and 3 ipads with my SO, and she doesn't need to be constantly bombarded with my semi raunchy work-guy friends group chats.
Basically all of my friends have migrated from using SMS anyway, and it is either FB messenger, or Telegram, both of which are multi platform, so if I wanted to have all my devices beeping in unison I could.
Every other use case I have is on a multiplatform service for cloud storage, photo back up, email etc. Even if I were using ios/mac os as my main devices, I need access from my work windows PC at all times, so I cannot use apple services.
Basically the only feature of the iPhone that's beyond reproach is the Apple watch. It's true it is far and away the best smart device on sale. However that's a pretty sad State when that's the only real positive thing that you can say on why you must keep an iPhone