Regarding the church marriage certificate and civil marriage cert, in Ireland from 1845 for non RC and 1864 for RC, the church authorities have been required to pass details of all marriages they conduct to the local civil registrar, who then enters them into the statutory marriage records. That way there is a comprehensive record of all marriages, no matter where they took place, for all of Ireland. (It doesn't mean that the couple went through a separate civil ceremony, which is perhaps what you were wondering).
The civil cert should say "Marriage solemnised at....." If it was a church wedding, the name of the church will appear, and for a registry office wedding, the name of the particular registry office.
The civil certificate is usually more helpful to genealogists as it contains additional information eg fathers names and occupations.
Can't help you with disp in Banns or your query re denomination.