Differences between a Non auto MCCB and Isoaltor

Anything that is called a "Circuit Breaker" (the CB in MCCB) is by definition a Load-Break rated device. That means that within it's stated withstand capability, it can safely open under load. An isolator makes no such claim. They are typically ONLY used when there is another device, such as a contactor, which will interrupt the load in all cases. The isolator is then opened with no load so as to just add an air gap of sufficient dielectric strength to maintain isolation for personnel working downstream. So if you were to compare an MCCB to a disconnect switch for instance, unless the disconnect switch specifically says it is a "Load Break" rated disconnect, it is just an isolator and cannot be used as a safety disconnect switch. An MCCB, whether automatic or not, is always rated for load interruption duty.

The reason why you see them used in conjunction with vacuum contactors so often is because a vacuum contactor can "leak" if there has been a fault.