Why use both Text Message Forwarding and Messages in iCloud? | Macworld
The interaction of these two features can seem a little complicated, too, depending on how they’re enabled:
Forwarding off, Messages in iCloud off: SMS/MMS messages appear only on your iPhone. iMessages appear on any device logged into the same iCloud account, as long as they are available on a network. Some devices may miss some messages. Forwarding on, Messages in iCloud off: SMS/MMS messages and iMessages are delivered to your iPhone and any other devices logged into the same iCloud account and currently online. Some devices may miss some messages. Forwarding off, Messages in iCloud on: SMS/MMS message notifications appear only on your iPhone, but are synced to other devices via iCloud. iMessage notifications appear on all connected devices and are synced among those that are offline when a message comes in. Forwarding on, Messages in iCloud on: Notifications for SMS/MMS messages and iMessages appear on all connected devices that are available on a network. All text and iMessages are synced to all connected devices.