The Thermawrap PRO seems more comparable, on paper, to the Arcteryx Atom SV hoody which I found to be very warm for the weight. So at 18oz, the Thermawrap pro packs a lot into those extra ozs. The older Thermawrap was 50g, so not as warm.
If you're looking for a lighter synth hoody in the 60g range, check out the Atom LT, which is 13oz. I prefer the Atom LT to the Nanopuff for several reasons, one being overall fit and finish. The Nanopuff is boxier in cut and the box stitching that holds the primaloft one in place tends to fray fairly quickly in the chest and arms from use. Both are really good synthetic layering pieces, I just find the Arcteryx to be a little more polished overall. Atom LT also packs down into a smaller package for storage in a pack, but not by much. If you can find the Nano in your size at a considerable discount, you can't really go wrong with it as a light weight synth parka.