Yes if an account is deleted the IP address, email and password are deleted. Their posts can remain and you can rename the user at the time of deletion eg to deleted member xxxxxxxx - if you want. Which is a good idea if their username is their real name or could identify them in some way.
To be honest if someone asked me for a file on what data was held I wouldn't have a clue. I'd probably just tell them - just your email, password and IP address. Or give them a screenshot of the IP address! Which is probably not GDPR compliant.