What happens when you're over the communication limit?

With the new engagement engine, our organization is taking the opportunity to re-examine our communication plans, but while we work on this, we would like to implement the communication limits asap. I understand how going over the communication limits would work in the engagement engine, but what happens in the event that the campaign is not part of the engagement engine?

Is the email in a suspended, limbo "wait step" until the lead clears the limit or does the lead just not get the email? When is the lead considered to have "flowed through" the campaign? The July release notes say "set a[n]...email limit and the system will do the rest," but what does that actually mean?

Also, for the weekly limit, is the "7 day" count based per week (S-S) or on a rolling basis (today is Tuesday so it counts emails from last Wednesday to today)?

And then to confirm, even if you "opt-out" an email from the communication limits, the email sent will still be counted toward the communication limit, correct?

Thanks for your help!