you should factor in the likelihood of losing some between acquisition and maturity. Very few people appear to get 100% survive to adulthood, especially if they were shipped. Two of my three homegrown summer clutches each lost a chick at about 3 weeks old (one vanished, one drowned) for example.
Fwiw, I had a couple of heritage LF RIR in my early years of chicken keeping, and they had no issues with the other breeds here. Can't speak to the other breeds you're contemplating, except to note that is it much easier to know who's who, who's laying, and to keep accurate records when you have hens that look different and lay different colour/size eggs. Also makes for a more interesting/attractive egg basket, and an option to select the right size egg for the purpose planned (when cooking).
Fwiw, I had a couple of heritage LF RIR in my early years of chicken keeping, and they had no issues with the other breeds here. Can't speak to the other breeds you're contemplating, except to note that is it much easier to know who's who, who's laying, and to keep accurate records when you have hens that look different and lay different colour/size eggs. Also makes for a more interesting/attractive egg basket, and an option to select the right size egg for the purpose planned (when cooking).