Best prctice to use multiple domains

I'm very much new at CWP. I have some domains and want to use WordPress, PHP scripts ...... I want to know what is the best practice to use multiple domains. Should I create separate user account for each domain or add all of my domains to only one user account?

You should create multiple accounts.
Wordpress websites are attacked very often, if you have all in the same user account, one bad script will have access to all other domains.