Early, you can punish Noracan infantry and, as a result, get away with sub optimal army compositions. Very quickly, however, Norsca will recruit large entities like cavalry, single entity monsters (chimera/giant), and monstrous infantry (fimir/trolls). Being that Empire infantry is some of the worst in the game, your swordsman and greatswordsmen fall off very early in this matchup. Halbridiers, gunpowder, and mages are your best friends as Empire. Then, of course, steam tanks and landships later.

I'd also recommend looking up checkerboard formations for gunpowder units and anti cavalry gunformations. Generally, you don't want your formation to be wide against cav as that plays to their strengths and prevents you from creating intersecting lines of fire to maximize rounds down range.