You may be asked to contrast two European or Irish regions, so you have to know both.
However, you can learn a full answer for a topic on one region and a half answer for the other in case of the contrast questions, usually in PEA, SEA and TEA. pick which one wisely. West probably has more for agriculture, Dublin for manufacturing and probably Dublin for tourism/transport. Similar for Paris and Italy.
Just learn one urban answer for one region for Ireland and same for Europe, as well as in pop distribution/dynamics. They'll just ask Irish region or European, not Irish peripheral or something like that.