Would it really take an Armada? Coronavirus infected 40k people, we have some of these viruses in labs. I’d send one agile team and drop a nice virus on Earth (minimal viable product).
The protons as you call them are a fun quirk of the science fiction genre, "How do we explain the Great Stagnation"? Fine Structure by Sam Hughes is the first book I've ever seen do it.
Maybe they’d have competition on the way here? I mean, if there is one intergalactic traveling life forms, why not multiple? Not that they have to be foes... but you can’t presume that they aren’t.