to the ones who don't fight it, it's more of a consciousness thing. Like the body will still exist and its more of a slow take over from what i've seen. The humans usually do have superpowers, but it's mostly phasing through things, phsychic visions, ect...
The incubation is the same as a human. We are made the same way humans are, except the ones on the ships and bases, those are taken out and tampered with.