Is Episode II another mostly Protoss campaign, or can we use different races?
Episode II is a hybrid, much in the same way that Episode I was. As for the “official” race of the campaign (usually distinguishable by what briefing background you get), Episode II is technically a Terran campaign, just as Episode I was considered Protoss. Again, there is a great deal of overlap here, so players will command both Terran and Protoss forces.