On cpanel you can setup many domains under just one account as long as you activate the addon-domains to the package of your user.
But, for security/organizational reasons I would advise you to install each domain under a diferent user.
If you need help with WHM shoot me a PM.
Or I can tell you how I would do it.
1- Create a reseller account on WHM(to avoid using root as a reseller)
2- Create hosting packages
3- Attribute packages to the reseller
4- Login to the reseller account
5- Create user/users
6- Login user(s) to cpanel and configure the domain(s)
thanks... will PM you.
'fully managed' dedicated hosting - super easy
shared hosting - super easy
'fully managed' vps - super complicated