Should I create my own password or generate password for Apple ID?

My own 2-cents:

Keep in-mind that your AppleID passphrase is sometimes CRITICALLY needed to be entered from memory - such as when using the “find my” to disable a lost mobile device.

While I strongly endorse the use of password managers, this is probably one of the few passwords you really DO need to be able to reliably regurgitate from memory while under stress.

AFAIK it’s not significantly length or character-type limited. A normal sentance - known only to you - using caps, numbers, and punctuation is one good method.

That is completely up to you. The Apple generated passwords are usually more complex, which is good for security, but make them harder to remember.

You are welcome.