Ahah! Okay I think I found my answer... I was confused by the terminology of "website" in enhance. Also confusion about what an Addon domain is, or how it's different from a regular "website" in the Enhance system...
In my testing I had added a second website to a customer account, which inherited the "package" limits as its own standalone website... What I should have done is opened the customers 1st website, then gone to Domains, then added an Addon site. THEN the addon site can not consume more system resources than the whole package/etc. in my scenario.
Wow, that's a really different way for me to think about customer accounts in relations to websites. I like it since it means I can let one customer account have multiple "containers" for their sites if they want to pay $ for it.
So for me to get a similar standard cpanel style setup, all my packages will have a limit of 1 "website", that way any additional "addon sites" don't get free bonus resources or whatever...
Boy, figuring this out was not easy. I'm glad this feature/capability exists, because I have many clients that have multiple cPanel accounts (so they can have dedicated resources to the sites in each different panel), so this capability can help make organizing things easier from a customers perspective... Just figuring it out as a host and the terminology messed me up 🙂
Hope this is helpful for someone else!