I'll go through my standard spiel. What are your goals? Why do you want roosters? The only reason you need a rooster is if you want fertile eggs. Everything else is personal preference. Nothing wrong with personal preferences, they can be powerful. I try to suggest you keep the minimum number of roosters you can and still meet your goals. That's not because you are guaranteed problems with more roosters but that the more roosters you have the more likely you are to have problems.
Flock balance? There is no magical flock balance ratio that creates a chicken paradise. It's not breed dependent either. There are so many different variables in individual chicken personalities, how much room they have, climate, how we manage them, ages of the individuals, and yes our individual goals that what works for one will not work for another. There are people that keep one rooster with a very few hens, one rooster with 25 to 30 hens, no roosters, or multiple roosters with a varying number of hens.
Flock protection. Boy, can you get varying opinions here. Some people seem to feel that a rooster will fight off a grizzly bear, others of us feel that a good rooster is mainly an early warning system and not much use in actual protection. In my experience a rooster does spend a little more time looking around so he is more likely to spot a danger and give warning, but dominant hens in a flock with no dominant roosters often take on that role. If something is suspicious he tends to put himself between whatever it is and investigate, and I have seen a rooster keep crows from eating some of the flock's food so they will help a bit. Some people have seen them attack small hawks. But I've lost chickens to dogs, foxes, a hawk, and an owl. I've never lost the head rooster. I have seen my roosters leading the flock to safety instead of forming a rear guard. My basic feeling toward how much protection a rooster provides is not much.
At ten months yours should be acting like pretty mature chickens. Males and females mature at different rates and there can be a huge difference in behaviors depending on maturity levels. Since the two males are coexisting now it bodes fairly well for the future.
If you want purebred chicks of both breeds then you obviously need to keep both roosters and you will need a way to keep the two flocks separated as any rooster will breed with any hen of any breed. If purebred doesn't matter to you then this need goes way.
When they are pullets and cockerels they may not have the best mating techniques. Those techniques usually improve when they mature. It's not that unusual for a cockerel to cause feather loss during mating. Occasionally mature roosters do. That is often where his claws are standing on her. Sometimes that is the back of the head. He grabs here head as a signal for her to raise her tail out of the way to expose the target. If the spots are bare and the skin is exposed there is a possibility his claws could cut her but if they are not that bare that risk is pretty small. If the entire feather is gone the feather should grow back before too long but if part of the shaft is still in there the feather will not grow back until she molts.
I consider your space fairly small for two roosters. If you really want more hens you can try to add a few but I wouldn't in an effort to get a better flock balance. If it is working, it is working. Adding new hens may just give them something to fight over.
