That's doable with CBSubs. CBSubs can assign a usergroup based off subscription state. It can also protect tabs/fields based off profile owners subscription status using CBSubs Fields Tabs Protection.
And last... two stupid questions: If I take advertisers out of the Registered group, then they should still be able to use the normal login procedures no?
Yes, if it's a parent of Registered. Example a follows.
Public
- Registered
- - Advertiser
How can I set in Joomla a module be used/seen by two ACLs? Or do I have to create two different ACL (Registered without Advertisers), Registered (with Advertisers)?
Create a usergroup (e.g. Advertisers) as a child of Registered. Next create a new view access level with only Advertisers selected. All Registered access will automatically inherit to Advertisers so they'll have standard access + whatever Advertisers view access level is assigned to.