It varies considerably : I've read from capital ship fleets colliding in the great wars, but Uni fleets are far more modest : mostly it is composed of like 5-10 BS/BC, 10 Cruisers and 20 Frigates and a scout or two. Each squad has some of those and within each squad you have different roles : BS/BC damage dealers, cruisers/frigs mainly tackling and ecm. When we encounter a couple of enemy BS the small ones scram and jam them and the BS/BC kill them.
But yesterday we went on a fast cruiser/frigate fleet alone, and we still managed to take out several small 2-3 BS fleets. I'm actually amazed corp let BS roam alone in losec, they should be properly escorted, a few drones alone clearly do not make the cut, they rather end up captured after their smoldering shipwreck gets salvaged :smoke: