The big deal is, having talked to security people, they are "fine" with WhatsApp because the theory is, they get data from whatsapp so they have some sort of backdoor access.
They are pretty chill with WhatsApp which id unexplainable
Maybe WhatsApp gives them a ton of metadata like all their contacts, when they chat and with who, IPs, etc. Signal only gives out either time registered or last used last time I checked.
WhatsApp uploads decrypted chats to the cloud once a week.
Source?
Have a look in the settings lol
No need to enable the google backup
Only if you enable it and theres a clear checkbox to enable E2EE. They should check it by default but I doubt even majority of people do backups.