True Patriot
Sanity is subjective
Different breeds is fine, as you see we almost all do it. I have 8 birds, 5 different breeds. As a general guide, try not to mix drastically different sizes, it can lead to bullying. Same for having an odd ball. Keeping a fancy breed with others can also lead to being picked on. Chickens don't mate in pairs. One rooster for every 3-5 hens is a good starting point. Too many roosters will lead to fights.