Where are saved passwords stored if you login to a browser, so they sync whenever you login to that browser on another device. Where and how do Google, Firefox etc. save the passwords? Obviously its not on ones own computer if you have to login to get bookmarks, passwords etc. synced. What if fx. Firefoxs servers where those password databases are stored are hacked. Are they then just up for grabs? And if so, is there some way to get Google or Firefox or whatever to delete all the stuff that they have laying around?
As with pretty much everything that is managed by cloud providers, secrets management as a service is susceptible to hacking attacks, HOWEVER, I would trust Mozilla's and Google's secure secrets management capability and infrastructure security in general much more than keeping those secrets on tools running on my machine.
To your last question, all major cloud providers offer you the capability of complete deletion of sensitive information they store, and are legally bound to fulfil that obligation when you are using their products.