I cannot add an AOL account to my Apple Mail.

One possibility is that you have two-step verification on your AOL account, and an older version of macOS. If so, you'll need to either create an app password for Apple Mail or upgrade macOS.

macOS Catalina integrates AOL's login page, which can handle two-step verification. It looks like this:

If you do not see this screen when you go to add your account – and you have two-step verification enabled with AOL – you'll need to either create an app password, or upgrade to a newer version of macOS.

You may have to delete the AOL account on the Mac & try again, the freaky thing is that there's no way to edit the say Password on any of the Auto setup Mail accounts, doesn't matter what PW you enter after that, the Mac Mail almost always chooses the old Passwords if you don't change or get rid of the old ones.

That's good!

No, you don't need to remember the app password. The only time you'd need it is if you had to set up Apple Mail again, for example after reinstalling macOS, and even then you could just create a new one.

Good news, great work, thanks! :)