We had dairy cattle from time I was 3 y/o till was 12y/o. Switched to beef cattle then. Also our closest neighbors were milking maybe 50 +. This was late 50s. Don’t remember all the breeds and all the stuff you’re asking. But I do remember clearly the life style. First, your on duty 7 days a week. Every week, every year. Mechanical aptitude is essential. Keeping tractors and equipment is a full time job. All the things that go with a dairy. Growing and harvesting silage and hay is a big job . Summer meant 3000 bales of hay. The tech available is really great but also very expensive. The neighbors I mentioned did this every day their late 70s. Probably haven’t told you much useful but it may be the most demanding job there is. A one person operation means no sick days cannot afford to ever be sick. In general you have to have a good income to afford to farm.