Welcome Joe-
I've only built one Warmoth, a strat, so I'm certainly no expert, but I've been playing for 50 years and done a fair amount of work on my axes over the years.
My neck came needing very little work. The fret ends were kind of rough, and needed a fair amount of fine filing to get them where I wanted them. The nut was cut way too high, as I expected, putting open chords out of tune. As I didn't have a proper set of files, I took the completed guitar to a pro to re-cut the nut. Cost me $40. If you want a complete fret level, it will of course cost more, but mine didn't require it.
My action is set low, <.050 @ the 12th fret on the low E string . Plays wonderfully. Just be careful during assembly, make sure the neck pocket is clean and that the neck fits snugly and flat on it's base.
I don't play professionally, but for me, the action and playability is right up there with the best of them.