What I'm hearing is that ... I have to manually UV map all my textures.

No, only the Vicky 3 figure. Remap the figure so that it has the same UV mapping as the original Victoria 1 mesh, and then all your old textures will work fine without further work. DAZ even provides the .uvs files, so it only takes a couple of minutes in UVMapper.

V3 cr2 to V2 cr2 - what's the point if it's just head morph transfering?

It allows you to use your existing Victoria 1 and 2 clothing with Vicky 3, just as the Victoria 2 P4 figure can wear Posette's clothes.