I couldn't find a list of "eligible charges", also that doesn't seem to mean advance payment would be the only payment option so I couldn't be billed and the service would just stop.. did I miss anything?

No, you didn't miss anything the advance payment is just an additional feature but you still need to give in your CC details so they can charge you if you make a mistake. The usual course of action is to stress out and beg them to forgive you, which they sometimes do, and sometimes don't.