Auto renew for check payments

We've got a site that has about 1/3 users paying manually by check and 2/3 online.
We would like to make available auto-recurring payments (we're using Authorize.net which does allow auto-recurring).

The question is, how are the check-payment users handled? Will they get a 'reminder' invoice to pay for the recurring amount prior to the expiration date or do we have to do that ourselves via other systems?

Also, what would happen if we turned on recurring payments for an existing plan (that is presently set recurring off)?

Would existing subscribers have any way to become recurring payments? Will they need to manually renew existing subscriptions as they expire and be given the option to switch to auto-recurring?

AND ... are notices sent out prior to recurring charges being made against the subscribers credit card? (or only when the card is actually charged)

There is no recurring payments for manual payments. Enabling recurring payments for a plan that previously did not allow recurring payments will do nothing for existing subscriptions except give the user the option to subscribe to recurring payments if optional or force it on the next manual renewal. Notices are not sent out by CBSubs unless you configure such a thing using CBSubs Mailer, but often the gateway themselves do (e.g. PayPal and Stripe both can).

OK ... thanks.