Arcadian French is a dialect of French spoken in the Acadian region of Canada. It's very similar to standard French, so there's no significant difference in the meaning or pronunciation of "mais oui" between the two.
However, if you're looking for a specific Arcadian expression that's similar in meaning to "mais oui," you might say "ben oui" or "oui ben" which are more common expressions in the dialect. These expressions are also used in other regions of French-speaking Canada.
Ultimately, "mais oui" in Arcadian French simply means "yes, of course" or "yes, certainly".