Interesting thing about firmness in the modern golf balls. What you feel is actually what you hear. Most are manufactured with very similar compressions and a ball that feels soft may be a muted cover material or a difference in the core material. Distance will mostly be dictated by dimple patterns and depth impacting spin although in the case of ProV1x, also impacted by multiple core layers and materials. Your last question about accuracy, yes, less spin means less side spin but it also means too low and you lose hight and carry. Less spin might help your drives but punish you on iron shots into the greens. It’s all about trade offs and finding the ball model that best suites your needs.

Firmness doesn't directly impact distance... and to a certain extent, more spin will help with accuracy. Too little backspin will be harder to control.