With living animals you don't get guarantees. We can tell you what is most likely to happen or what we expect but things don't always go as we expect. Most of the time cockerels raised together in a bachelor pad get long fine. They will sort out a pecking order but so will pullets raised together with no cockerels around. Often this is very peaceful but occasionally it can get rough, whether they are all pullets or all cockerels.
Each individual pullet or cockerel matures at its own rate. They sure cannot read a calendar. I typically raise around 20 or so pullets and cockerels together with the flock with my first hatch, then mix more in later as hens go broody and hatch. I'm in a totally different situation than you, cockerels and pullets together and them various ages, plus adults mixed in. With one exception they don't kill each other.
One time I bought 20 cockerels as baby chicks and raised them with the flock. When they were about 15 weeks old one took an intense dislike to another specific cockerel and killed it. That was it, that killer cockerel got along with the other cockerels. Oh, they had their dominance fights but none go hurt. Those fights were no more serious than any other year. I've seen a lot of cockerel fights over the years but that is the only one that I've seen where there was even a serious injury. I eat mine around 23 weeks, that's why I raise chickens, for the meat. If I kept them longer my story would probably change. I'm telling this story to show you really don't get guarantees with living animals, things don't always work out as we expect.
Your situation is different from mine. With two cockerels and two pullets you are probably wise to separate them. I think that gives you the greatest odds of success from what I think are your goals. From what you describe with those random squawks it sounds like they are establishing a pecking order. The dominant one is surprising the submissive one with a peck. The submissive one accepts it and does not fight back. It's pretty peaceful way of establishing the pecking order.
Since they do mature at different rates it is possible the submissive one will mature to a point it will challenge the other for dominance. This may never happen but it may. If it does you'll see them squaring off, facing each other and trying it claw or peck each other. It gets pretty furious for a short bit. It's possible one could get hurt, they really are trying to hurt each other. What practically always happens with mine is that really quickly one decides it is better off running away instead of fighting. There may be a repeat performance or two but they've pretty much decided who is dominant. I'll repeat, other than that one time, I've never had a cockerel seriously injured during this phase and that is with pullets present. Other people have had different experiences. You don't get guarantees.
How can you tell it will get serious? You can't until you see an injury. If you interrupt them before it is settled they will settle it later.
In your situation with no girls to fight over it is highly unlikely they will get serious at all. Highly unlikely but I can't give guarantees. I also can't guarantee that you won't see worse between your two pullets as they determine which is dominant.
