If you want to hear, Invaders are an always hostile Alien race that appears through wormholes, I don't know more, they somehow avoided me so far.
Star Swarm seem to be self-replicating fleets of tough motherships housing 10000km/s fast 800t gunboats with a meson cannon, which I never fought aswell, because the only time I encountered them, it was an unarmed ship without actives, and I didn't want to take risks.
I think the Exodus Campaign (Aurora Fiction) has an engagement with the latter.