Redleg- you got it mostly correct.
– Soft Cheeses may use (microbial) Rennet, but since they don’t “have” to, the hashgacha agencies are lenient.
– Most Vinegar in the USA is actually from Corn based alcohol, or Chemical/gas based. Some from Wheat or Apples, while a minority from Wine.
– Your NB point- Who are those poskim that don’t require a hechsher on regular cheese that contains multiple ingredients including rennet, albeit mostly microbial (- I saw animal based rennet used in cheese production south of the border…)
Jewish Thinker- Shulchan aruch heter is only for Butter, not cheese. Although today you can have 100% cream (churned into butter) which may be 100% non kosher, depending on the cream source [e.g. cook water cream from cheese production, ie. gevinas akum, or whey cream, blended back with pure milk cream]
A complicated “sugya” that we in the kashrus industry have spent lot’s of time on.