Could you expand on this? At first it sounded like you were saying that it won't make a difference if it's password-protected or not.
Sure 🙂
The default method of password protection used in Windows uses a system called ZipCrypto. This method will stop you from extracting the contents of a zip file unless you have a password, but you can still inspect details of the contents including the file names.
So if you have e.g. a Pirates of the Caribbean edit called "Pirates Of The Caribbean - More Booty Edition.mkv" in a zip file protected with ZipCrypto password protection, anyone who downloads the file knows what the filename is - whether or not they have the password.
If you use the .7z format instead of .zip format in software like 7-zip, you can use AES256 encryption as part of password protecting the file - this is a much more robust form of encryption and does not disclose any details of the file contents until the correct decryption password is entered.
Spanned files are just my preference in terms of it being easier to resume upload/download of a file split into 250MB or 500MB chunks than it is an entire file in one go.
Edit: Another thing I forgot to mention is re: password reuse. The article I linked casually mentions that the new scanning system Microsoft has deployed will scan messages with zip attachments for possible passwords to use, and if those do not work it will fall back to using a list of known passwords. This means that having/using a default password as has historically been the case would make it easier for the password protection to be rendered ineffective, since once the password gets on the list all future edits would likely be checked with it.