Board Thread:Naruto Discussions/@comment-33485854-20180907234534/@comment-1872728-20180913153656

This is how I understand it:

V1: Human using Tailed Beast chakra V2: Human and Tailed Beast hybrid Tailed Beast Mode (V3): Tailed Beast

and...

- KCM1: Human using Tailed Beast chakra - KCM2: Human and Tailed Beast mix chakra (essentially hybrid) - Tailed Beast Mode (KCM3): Tailed Beast

So essentially they're the same, but the KCM line is just the V line while transforming the body into chakra as well. The reason Naruto uses the KCM version is because it has phasing abilities (shown in The Last when Naruto puts his whole arm into Hinata's chest). At least that's what I think.