I have bulls next to each other, I prefer young ones, or at least having a young bull next to an older one. On a side note I try to keep them at least a field away from neighbors bulls, if my bulls get in with each other, it's nothing but a little more work, but if they get with other herds it can be a plum mess.
As far as certain breeds causing more trouble, I will say that they are all bulls. I have noticed that the Angus I have had have been rowdier at an earlier age than the Charolais or Hereford bulls I used to have. Had a Charolais that didn't try to get out until 4-5 years old, and had a Hereford that when he hit 3, would stand at the fence and beller to get the neighbor's Charolais bull to come fight with him. Had a year old Angus bull this year, that bellered around and got my 2 yr old Angus so worked up that he wouldn't stay in his field, so now both of those bulls are gone,
I would also advise caution with a Jersey bull, they can be extremely aggressive at an early age. I would recommend a low birthweight Angus bull that seems to have a good disposition.