Should I repack the hub bearings on new wheels with quality grease?
You may want to just open them open to take a peek to make sure that: 1) they are actually packed with grease to begin with and 2) that all of the bearings are actually there.

With cheap hubs, missing grease and missing bearings are not unheard of. But if a quick peek yields lots of grease and a full set of bearings, I'd tighten up the cones and pedal away.

[New]  p.s. Just a quick note that asking which the best grease to use is sort of like asking which operating system is best: Windows, Linux, or MacOS (or FreeBSD or AmigaOS). You can't go wrong with whatever the LBS has (Pedros, Park, or even FinishLIne). I tend to be a quirky FreeBSD type and use Magnalube, a weird specialty lube which no one else has heard of.