How does the parallel redundant UPS configuration differ from an isolated redundant UPS configuration?

A parallel redundant configuration is considered N+1 and an isolated redundant configuration is considered 2N.

A parallel redundant configuration requires a static bypass switch and an isolated redundant configuration does not.

A parallel redundant configuration eliminates downstream single points of failure and an isolated redundant configuration does not.

A parallel redundant configuration requires models of the same capacity from the same manufacturer and isolated redundant does not.