I agree about the RIR's re hatchery vs heritage breeder stock. I've raised quite a few hatchery reds, they have always been my tamest birds as far as how they relate to people but they can be aggressive with other birds, more so I think when you try to integrate new birds into the flock. Mine were always completely fine with the birds they were raised with as chicks but they were the most aggressive when I brought in new birds. My hatchery reds also seem to be the shortest lived birds in my flock. I seem to get a high rate of egg laying/reproductive tract problems like EYP and internal laying with them. My last two hatchery reds both barely made it to their second birthday.
I've kept one hatchery Rhode Island Red (Production Red). She hasn't been mean, but wasn't as sociable or personable as my Wyandottes and my Easter Egger. I haven't kept Australorps or Orpingtons, but many members consider them to be docile and gentle, as well as good layers. They may be a better option than Rhode Island Reds.
Welcome to BYC. Glad you decided to our flock. I've raised dozens of breeds over the past 50 years and I concur that RIRs are sometimes aggressive (especially the roosters). If you're going to have a mixed flock, I would suggest starting with breeds than have a well deserved reputation for being calm and gentle (potential lap pets) such as Australorps, Orpingtons, Brahmas, Cochins, Sussex, and Faverolles. If egg production is a priority, Australorps are the best layer on this list, and Cochins are the poorest layers (although they are the best brooders and mothers). Please feel free to ask any questions you may have. We are here to help in any way we can. Whatever breeds you decide to get, good luck with your flock.
Many breeds "work well" with Rhode Island Reds or Production Reds. Some breeds that probably wouldn't get along include Polish, Silkies, small bantams, and other crested breeds. Those breeds are either rather delicate to live with boisterous Rhode Island Reds (Silkies and other bantams), or don't interact well due to sight-problems (crested breeds, Polish).