I have about six cages-all from my previous ownerships
Originally, two large Rotastak cages were connected together with a big tube between the cages. Each cage has its own wheel, water bottle and a nuts bowl.
I have now re-arranged to tubes, to each one has a maze to herself. Added toilet/bath and fresh food bowl to the 2nd cage, where Hetty is now residing.
They are now both quieter. Hetty seems to eat a bit more, which will be perhaps noticed at a next weigh in in week's time. Currently, she is 31 gs.
Hetty does not run as much as she did before separation. So she should put on a bit of weight. They can still meet when out in their balls.
Update in week's time.
In the past, I have had exclusively Campbells males. All from reputable breeders, pre-tamed and friendly. I have had up to 5 cages strung together with mazes of tubes and hideaway, used by 4 brothers. They have never argued or fought. They very often ended up all 4 together in one wheel, resting. When out, they would all sediment to their favourite space in my bedroom (I have one level flat), in line, either chatting or resting. It was always rather sad, when life progressed and they went over the rainbow.