wanted to know if it would be alright to mix breeds?
All those are all regular dual purpose chickens. You don't have any with strange feathers (like Silkies) or weird things growing around their heads (like Polish). Your integration issues will be the same as if they were all the same breed and color. Lots of people have Silkies and Polish in with their dual purpose birds without problems but some people say they can cause issues. I sometimes wonder if it is their integration techniques that cause those issues because so many others don't have those issues.
My first flock was red and yellow, black and white. Speckled Sussex, Buff Orpington, Black Australorp, and Delaware. No issues at all because of mixing breeds or different colors. Your integration issues will be from mixing chicks with adults.
I don't know where you heard that Red Stars can be more aggressive. Red Stars are not a breed, it's just a marketing name for red sex links. Some Red Stars are made by crossing two different dual purpose breeds. These should act like other dual purpose breeds, no better and no worse. Some are based on the commercial egg-laying hybrids. These are bred to take confinement well and get along with other birds even when housed in pretty close conditions. Black Star is also a marketing name, it just means a black sex link, could be a commercial hybrid or a cross of two dual purpose breeds.
The differences in aggression that I've seen is not because of breed. Each chicken has its own personality. Different chickens of the same breed can be way different in aggressive tendencies. Housing them too close together can bring out aggression from any bird. Differences in age (maturity) can bring out aggression, it doesn't matter what breed they are. You can get the same issues whether they are all the same breed and color or if they are mixed.
I like your mix, you should enjoy them. Good luck on integration.
