From everything I have read you are correct. You can follow the universe rules on resources and other items and link your rented planet to the existing universe. You will be able to limit who can visit and who can build. I am hoping you can limit who can gather and mine but that has not been mentioned by the developers. If you wish to have a planet that does not follow the rules, such as having gems grow on trees or indestructible tools, your planet is not connected to the public universe and you cannot move resources into the public universe.
I will not disagree that there will be some movement of people to the rented planets. If you want to control your build and the environment around the build you really have few options. You have to use an enormous amount of plots or rent a planet and use limits. I think it can be good for the game as the rentals add revenue to support the game, it does prevent a good deal of the issues with the neighbors, and more planets might mean more sources for various resources.
I think that an in-game messaging system to allow players to communicate with each other would be helpful, especially since you may not see the other player in person. Most problems are caused without any intention to be hurtful or disruptive to other players. And with a limited ability to reach out to other players in game, unless they are playing in the same area at the same time, miscommunicated turns into frustrations, retaliation, and griefing. Opening up a mail system for private communication with players to access perhaps at beacons would be super helpful to allowing players to resolve problems.
It won’t solve every problem, but it will help when the harm is unintentional. A few issues I have had were easily resolved when I was able to talk with the players in game.
