If you search for Scott Hanselman's Penny Pinching blog post series, he details how he runs a couple of his high volume sites for as cheap as possible in Azure.
This. It is very comfortable to use Google OAuth sign in, even if you have a custom domain, but I've run into a few services that will not let you log on with user/password if you created the account via Single Sign On with Google, regardless if you use the same email.
Are there cases where users have taken Google to court to get their data back in this case?
I've had my Gmail account since 2004 and I am also terrified about this. I ended up re-registering my custom domain and putting it on M365 but still... it feels like, as another commenter suggested, there should be laws to allow any customers that were banned or terminated from at least getting their data via Takeout
Do you really think that they have no way to tell that it's you between all those accounts? I mean, there's no really a concept of account linking between Google Accounts, but between your IP being on all the accounts, and browser or device fingerprinting, I'm not sure this is really a reliable fail safe. It should be, but I doubt it.