I know this is a meme, but security is not binary. It is not you either have 100% or 0%, it is always a sliding scale, and usually on the opposite side is convenience.

Encrypting your drive protects against someone stealing your computer or breaning into youe house while the computer is off/locked.

People like to trash people that write down their passwords on a post-it note and keep next to their computer. It is not ideal, but having a somewhat complex password written down protects a lot more against attacks over the internet than having "password". However, if others have physical access to the note then it is obviously very bad. Like for example in an office.

Encrypt whole hard drive?
Yes.

Log in automatically?
Yes.

@mycodesucks

Heh, I have done just this for a friend of the family on Linux mint Debian edition.
It works out alright but I always feel weird setting it up.

I had made a little mistake after attempting to try out the experimental Cinnamon Wayland desktop on said machine & failed.

... Then boot looped ... Because autologin was setup.

Tiny bit embarrassing. Oops. Better keep backup minimal CLI Linux installs to repair/restore on seperate partition but seperate drives are best.

Is there any OS that allows this config?

At least with Linux, if I encrypt my hard drive, I have to enter my encryption password on every login, for some even during boot.

Not sure about Windows. I wpuldn't be surprised if you can have bitdefender on with auto login.