I have only used the HDR mode on my D800 but I assume it has similiar functionality. It worked really well for interior shots but less impressive than multi-shot HDR using bracketing when shooting in wide DR outdoor scenes. With the D600 and D800, HDR is not really needed unless for special effect since exposing covering the high tone range means shadows will still have enough color and detail to bring up in post with just a tone curve adjustment, which out the potential problems of ghosting and needing a tripod for multi-shot bracketed HDR conversion. HDR is a lot more useful on my D90 than either the D7000 or D800 which both have amazing DR at low ISO, as does your d600. 14 stops is a lot of tone range and only dreamed about a few years ago.
Regarding metering. To make sure you have the ranges covered, using Matrix would help in making sure you have enough headroom for the highest tones. Spot or CW would be effective if you did not have the great range of tone levels(or spot metered on the high tone), but then again, why use HDR then? Stan St Petersburg Russia