i'm sure its hidden somewhere within these threads, I've spent several hours looking but would appreciate if someone could explain the differences between these NAVS and also how they relate to NAVCORES?

NAV1 is the first generation of TomTom devices, NAV2 is the second generation of TomTom devices etc etc. NAV1 & 2 devices use TomTom Home software but NAV3, 4 & 5 use the TomTom MyDrive connect software for administration.

TomTom provides each device with it's own specific navcore which is always the preferred option but in certain cases you can use a specially modified navcore created by somebody in the community that will allow a different navcore to be used on another device for some extra features or stability. Always do a full backup before making any changes so it's very easy to revert if necessary.