most of those chinese device can't use outside china... for example some of my xiaomi devices need to connect to the china server in order for it to work / view in app.

thats why i say some, not all devices. some "dumb" devices that dont require app to use, you can use it anywhere.

as for changing the server, can be quite troublesome. for example, i have mixture of device from china and international. i can't use the manage both devices at the same time because of the location setting.

i also have a device (non-xiaomi) that can work without the app, but with app you'll get more features. but in order to use the app, you need to register with a chinese phone number.