The only breed you could get to create sex links with a buff rooster (as far as I know anyway) is a barred rock. That will create black sex links, but only if the mother is the barred rock.
As for not wanting to mix certain breeds...that may be very true if you are breeding with a specific purpose in mind. But for just plain old barnyard mix chickens there aren't really any breeds that when bred together will cause any problems. The breeds you have won't give you sex links, but they will give you plain old mixed chickens who will probably lay ok and may or may not be useful for meat birds (nothing will give you a meat bird like what you buy in the store, but you can eat any kind of chicken...there are just some that most people don't find worth the effort to raise to butchering age because there will never be that much meat on them).
As for not wanting to mix certain breeds...that may be very true if you are breeding with a specific purpose in mind. But for just plain old barnyard mix chickens there aren't really any breeds that when bred together will cause any problems. The breeds you have won't give you sex links, but they will give you plain old mixed chickens who will probably lay ok and may or may not be useful for meat birds (nothing will give you a meat bird like what you buy in the store, but you can eat any kind of chicken...there are just some that most people don't find worth the effort to raise to butchering age because there will never be that much meat on them).
