You have a couple options...
if they're dual purpose birds for meat, you can keep everyone together and slaughter each bird as he becomes an issue. The pro to this is you don't need a separate pen. The con is you have to be available to slaughter fairly quickly if a young guy gets crazy hormonal and you have no alternate housing.
you can also pull the males as they become apparent. When I do this, I have a large-ish grow out pen and add cockerels to it as I become confident of the gender. I don't have an issue with them fighting as I add more birds, usually because I can sex fairly early and they've been raised together. I also have lots of space. I also have the option to run a mature rooster in the grow-out pen to keep the young guys in line, but understand not everyone has that available.
They don't become bullies to the pullets, but they do reach sexual maturity faster and want to mate sooner. More than one or two cockerels can easily gang up on a pullet and make her life pretty miserable. However, by the time those hormones are flowing that hard, it's readily apparent who is which gender, usually around 4 months or so. Dual purpose birds are usually slaughtered around 5 months, so you're already close to your butcher date when they start getting randy.