The only thing I remember reading is that not every country gives you a NON imm OA visa every time. You have to check this with the Thai Embassy in y'r home country.
Don't think so concerning the last bit. After that second year (need a re-entry permit if you want to leave and come back) you can ask for a year extension (with health insurance of the whole period of that year extension). So the only difference between a year extension based on NON imm. OA and NON imm O is that health insurance requirement.
Aha, there are 2 different visa's they call long stay. The non imm O-A indeed, but here we talk about a non imm. O, so without the 'A' ! That's maybe the misunderstanding. With the non O-A you immediately can stay for a year. Also 1 extra year with a border hop just before that first year expires, when you have y'r healthcare insurance covered for that year.