Concerning the probable arrival of an alien race in the future, my opinion is as follows. Aliens, if they exist, will eventually come to earth, if for no other reason than curiosity. Whether or not they will conquer earth is the subject of this dissertation.
First, and most importantly, earth is not your run of the mill planet, by all accounts. Our moon has had a tremendous effect on the inhabitants of our planet. It is too large, in the classical sense, to actually be a moon, and that could make our planet unique. Or at least move it into the range of unusual. Some scientists even call it a companion planet, instead of a moon. Two thirds of our planet is covered by water, and that may also be unusual. It may be that life itself is unusual. Whatever the truth of the matter, aliens are probably more likely to be very alien. Maybe they don't have the ability to eat what we call meat. As herbivores, they would have different motivations and would react differently to stimuli. It almost a certainty that they couldn't eat the food on our planet, nor could they drink the water. Things in our water would make it unpalatable, if not downright dangerous for them. If they were evolved from a non-violent species in an ecology where survival did not depend on competition, they might actually want to help us improve our lives and society.
In any situation, as rational beings, we must apply logic to attempt to determine an outcome. The more valid the logical premise, hopefully, the more correct the prediction of future events. We need to ask ourselves why aliens would want to conquer earth. One possibility is for the power that comes from ruler ship. That usually applies to humans, but how about to aliens? We, as people, seldom have any desire to rule' other species. Ownership is different, and makes a good argument for aliens to come and conquer. If they look into our history they will probably pass on that one. Humans have a long history of not allowing others to own them. Perhaps out of a desire to have a slave population, but that goes back to ownership, and we explored that. Maybe they have a society that requires one ruling class and everyone else below that. Such a thing is possible, and has occurred in human History.
It occurs to me, however,. that the rules which have governed societies on earth are gradually improving. It has only been a couple of centuries since humans discovered freedom, as a part of government. Slavery used to be considered a part of society, now it is rare. The existence of absolute monarchs used to be common, and it is rare as well. We probably cannot imagine the system of government that aliens will have adopted. Aliens might have some version of the 'Star Trek' prime directive, or if not, will at least feel obligated to 'improve and enlighten' the lives of the savages. We, as humans, have not had notable success with attempts to do this, primarily because we have often (always) failed to consider the culture of those we are 'assisting'. We can only hope that the alien race which finds us will have had similar disappointments and learned from them. If not, we can always provide them with a detailed history of our efforts, and all the things we did wrong. At the very least they could show us ways to improve the social and legal structures we have, and maybe even show us a form of government that didn't make us want to kill each other.
Now I'd like to deal with the issue of control. Aliens won't need to control humans. They won't want positions of authority, in the sense we have them. Aliens will be separate and not equal. I can scarcely imagine anything that an alien could want from us, especially considering that there are many empty worlds, (if there weren't we would have noticed the by products of intelligent life) and it will probably be very hard to cross interstellar distances. What could be that valuable? Nothing that I know of, except friendship, would be worth that kind of effort, and that requires the aliens to be in a non-hostile mode. Non-hostile aliens might be a good thing.
Another point I want to make concerns alien technology. It would not be 'imposed' on us; we would have wars to obtain it. Humans would fight and die to have things that the aliens considered mundane. Aliens might destroy human culture, and many humans might perish, but it would be due to our insatiable greed and covetous natures. The problems facing the aliens would not be how to take over the earth and subjugate its peoples, but how not to do so. I suspect they would spend much time and effort in trying not to disrupt the ebb and flow of human life. Like those who deal with animals in the wild, they would try to promote safe habitats and limit contact with other aliens. Human beings realize that other animals have a right to share this planet, with the exception of a few people who are, as I mentioned before, greedy. Aliens would probably view us in the same way. A bonus would be that there isn't a market for captured humans and probably never will be. Historically, we make lousy pets. We've come back to that ownership thing again.
Finally, I should note that Humans, and probably aliens as well, prefer uninhabited regions to colonize, when such are available. With the wealth of planets in the galaxy, and the difficulties inherent in an interstellar war, I suspect the aliens would much rather use an empty planet, than face the challenge of colonizing one that has life as nearly intelligent as ours.
That speaks to the intelligence thing, and it is vast. Aliens may have intelligence that dwarfs ours by comparison. What are insoluble puzzles to us may be children's games in their society. There are hundreds of science fiction novels on this, and I won't bore you with the details. Suffice it to say, aliens probably won't care two figs about our planet, unless they see us as potential friends, or subjects to be studied. The Klingons of Star Trek' notwithstanding, there is very little to be gained by traveling across the galaxy in search of worlds to conquer.
The only possible exception I can think of is one found in the movie "Independence Day", which proposed a race of aliens that were like locusts, traveling from world to world and devouring everything. That premise also appears, repeatedly, in Science Fiction, and has been debated for at least all of my life. I don't see it as valid, because the resources of a planet which has little or no life on it are probably easier to get and vaster, not to mention more easily adapted to the use of the invading race. Only creatures that feed on other intelligent life forms would need to invade and conquer a planet that had intelligent life, and they would not be interested in the survival of the conquered race, except as a renewable food source. That might be a scary thought, if one concedes that consuming intelligent life could satisfy an incomprehensible need of an alien species.
In short, we probably have much more to worry about concerning our fellow human beings than we do with respect to an alien species that might come and take control of our planet. We will probably destroy ourselves in some cataclysmic war before the aliens even get here. That is if we can avoid polluting the planet and stop creating an ecosphere that is hostile to human life. Microorganisms, such as Aureococcus anophagefferens, have been known to grow until they actually kill themselves by overpopulation. As humans, we could do that. I'm certain that whatever a microorganism can do, we humans can do at least as well. If, however, there are intelligent aliens, and they do arrive in time, they just might save us from ourselves. Unless they have regulations in place to prevent it.