For example, let's say a man who immigrated from India as a teenager with his family gets married to an Indian woman. They are both Hindi, and the marriage is arranged. In their culture, this is perfectly normal. So then what is also perfectly normal is a very large wedding over several days with many different rituals and steps. The visa officer will expect to see evidence that the marriage was arranged, and that a culturally normal wedding and reception was held. If they do not marry this way, they had better explain why upfront in the application.
A couple from Canada and Ireland would not have this cultural norm. In their case, it would be perfectly normal to have a big, lavish wedding, and it would also be perfectly normal to have a small civil wedding, or a small religious ceremony with only a few family members and friends. For any of these choices, the visa officer will not be suspicious. I suggest you make even the simplest ceremony look special: get dressed up, exchange rings, have flowers, have some family and friends, have a reception after even if it is just dinner at a restaurant with your witnesses, take photos, and go on a honeymoon. Anything less than that will have to be explained, but probably will not hurt your chances of getting PR.