Earlier quoted context omitted.
Then buy an iPhone, and turn off iCloud Backup in Settings, it's not hard to do. Then your iMessages are fully E2E Encrypted.
Nope, because they get escrowed by the other end of the iMessage conversation. Also, the whole point of disabling iMessage (in this thread) is to close the iMessage-related zero click exploits described in TFA.
And are you really sure that Signal or your preferred messengers don't also have Zero-Click exploits? After all, they aren't sandboxed to the degree iMessage is with BlastDoor.