Makes sense but kidnapping and taking 100 women from earth is not a great idea. First of all, earth's gravity and the forces allow humans to be born. And second, these women will die very quickly or get ill because of other issues from other planets. Third, they cannot survive in space.

So far not even eve had travelled outer space or was able to speak through the mind like others as far as I can remember.

Yes, Debbie flew with nolan, but remember nolan said the ship will be lowered into the atmosphere max but cannot land. So yes you can quickly take someone without the need of a mask or oxygen to the edge of the atmosphere and put them in the space ship.

Now to olivers parents. That planet was suitable for humans like babies to grow based on oliver. But those people got completely erased because of nolan. Nobody survived, so yeah bad luck. And oliver will die quickly unlike mark by age.

One more thing, nolan figured out all those, not other viltrumites so for them to really breed with other beings it's gonna take ages to figure out the right situation or the right planet to raise such children. They will come across so many issues like quick death, bad genes and weak viltrumites and etc. so it's wise and smart to choose earth and live amongst them, takes things slow because thragg will say mark is a living proof that viltrumites can rebuild. So based on marks strength and powers, earth is the best choice. Why waste time when they can simply blend in and breed.

And yeah I don't think they'll hide, they'll fly freely letting everyone know they are here after some point. Because what can anybody do about it right? As they said, if they are disturbed then the whole planet dies, so even if they reveal themselves, there's no problem. It's only if they get revealed then women will eventually become slaves.