Re: String Action Height and Sustain.
In the end, it all boils down to preference. Some of my guitars have very low action and I don't mind a hint of buzz in them, because I'll play them mostly heavily distorted.
But for example with my 339 and my Tele, I want every note to ring out clearly and clean since I'll rarely distort them as much as my Ibanez guitars, so I'll keep the action a bit higher on them and it works nicely.
Also, if you do a lot of bends and vibrato in the style of Marty Friedman, Brian May, Ritchie Blackmore, Gary Moore, Peter Green, David Gilmour, etc, you'll find that too low an action will make those big bends a bit more difficult. So you'll probably want it at least "low-medium" and not uber-shreddy low.