I think (some correct me) you can group most devices into the following categories:
1. Device requires internet for setup, and for usage
2. Device requires internet for setup, but after that don't need it anymore
3. Device can be fully setup without internet, and used without internet
Personally I aim to be fully within 3 as much as I can, but some devices are really hard to find at a good price point that falls into 3. All my HA devices are within 3, except some real-time cameras which I couldn't find below ~300 EUR if I wanted them in 3, so those are within group 2 and now isolated after the setup.
1. Device requires internet for setup, and for usage
2. Device requires internet for setup, but after that don't need it anymore
3. Device can be fully setup without internet, and used without internet
Personally I aim to be fully within 3 as much as I can, but some devices are really hard to find at a good price point that falls into 3. All my HA devices are within 3, except some real-time cameras which I couldn't find below ~300 EUR if I wanted them in 3, so those are within group 2 and now isolated after the setup.