Making yogurt at home is one of my new hobbies. As I understand it, Bulgarian yogurt is like a "breed" of yogurt since cultures that originated in different areas have differences in taste, thickness, etc. Greek and Bulgarian are the Ford and Toyota of yogurt.
I'm making my second batch today. When I bought the culture, I looked for one with more than 2 species of bacteria although there are 2 that are considered the definitive ones.
For the first batch I used mostly whole milk with less than 1/4 cream. In my mind that was "really" whole milk since milk seems thinner today than I remember from the past. I found the flavor pleasant without any sweetener although I added some fresh fruit and some of my water kefir grains (taste sweet but as I understand it they're not that digestible.) The consistency of that batch was very smooth, about as firm as nice whipped cream.
Today's batch will be half milk and half cream and the third will be 100% cream to see how the consistency/flavor varies.
UPDATE: After testing, I found the smoothest, creamiest yogurt is a 3:1 ratio. For each 3/4 c of whole milk, I add 1/4 c. heavy cream. My favorite thing about making yogurt is that it still tastes like a dairy product--rather than thickeners, texturizers and preservatives.