1) Yes, if you program new DCF client with LOCKSTEP_EN = 0, it makes checker core as independent.
2) Yes, it’ll behave as second core connected over separate XBAR port.
Programming of DCF records is not trivial task but it is manageable. User would be aware that he can easily destroy the chip in case the programming is not done properly and the device may never exit from reset. It is simpler to order S32K324 that have decoupled cores by default, in other aspect it is the same.