How to set up diferent password rules for regular users and for root on PAM

Question

Bear with me for a moment. I'm doing a college exercise setting up a VM and I'm having a very hard time understanding what PAM is and actually works. All the results that come on google are either too basic or too complex and I really don't know what to look up. My exercise requires me to set up a bunch of rules for both normal users and root:

To set up a strong password policy, you have to comply with the following requirements:

• Your password must be at least 10 characters long.
• It must contain an uppercase letter and a number.
• It must not contain more than 3 consecutive identical characters.
• The password must not include the name of the user.
• The following rule does not apply to the root password: The password must have at least 7 characters that are not part of the former password.
• Of course, your root password has to comply with this policy

I haven't been able to find any good sites that explain how PAM works in a good way however I found that for the normal user I need to edit /etc/pam.d/common-password with:

password        requisite          pam_pwquality.so retry=3 minlen=10 ucredit=-1 dcredit=-1 maxrepeat=3 reject_username difok=7 enforce_for_root

Although I don't understand how PAM works I do understand it's flags. My question is how do I set up different rules for root?