Is it possible to add these accounts and devices to the hub without placing me on their devices and vice versa?
Now I get it!
You want to know if you can use the Home Hub as a shared device that both of you use with all of your respective lights and chromecasts. You want to use it as a hub, literally.
I typed a whole answer than I just deleted it. I should make this one point that might answer all your questions. I think the name "Hub" is misleading because it sounds like what you are asking to do. The Google Home Hub is just another device in the series. So, you have the Google Home, the Google Home Mini, and the Google Home Hub. They will all exist in your account the same way. The big difference is that the Hub is going to have some additional settings because it has a screen. I didn't notice any difference in the actual, initial set-up of my Hub. Exactly the same process as a Home or Home Mini EXCEPT there were some additional steps because it had a screen.
The Google Home devices are designed to have multiple users (I think six). Each user can connect to it using their own Google Home app. Any devices that are associated with the account will become shared. As far as I can tell, I can't, for example, lock my husband out of controllling my office lights. I just checked his phone and it shows everything in our house, including the Home Hub I added two weeks ago.
That sounds like it's something you don't want to do with your house-mates. If you are seeking to keep your other devices from becoming accessible, it won't work. If you don't mind, you can probably have someone take control of everything, then everyone else becomes a user.
This is my understanding. Maybe someone else will chime in with a solution that I'm not aware of.