Beeman, there are not stupid questions just stupid people...like me. But I digest.
Ok, so you just asked the most important and most interesting question of all. How do I begin? Yes all meso based and thermo based starters are the same (pretty much), the same strain of bacteris that is. They change sugars and other substances into lactic acid. Ricki's Carroll book sucks...there I said it. When it was new back in 1982 it was helpful and not so pretensious, now the new edition, 2002, well let's say it sucks...again. This is not a book reveiw and I plan on doing one to correct her many mistakes. I digest... There are many recipes that use different cultures to produce different cheeses, but what they all have in common is they have to have either a basic meso or thermo with it. So for Parmesan I use TA61 thermo and LH100 an additional thermo for hard italian cheeses. What sets each cheese apart from one anther is a complex subject that my fingers can't handle the full explanation but I'll summaize. Heating temp, amount of acid produced, milk type, milk fat content, pressure, aging conditions, other molds or bacteria, cooking time, curd size, cooking temp..all these variables produce cheese that are vastly different cheeses. I know it sounds like a miracle to produce cheeses that don't look like their from the same food group, but just think what can be done with eggs, water and flour..you get bead, cake, matzah and a million different things. I hope that helps.
