So if I take it to my Luthier, tell him I want it setup at medium height with standard tuning, there should be no issues? I take it a Luthier can make it work so the sustain will be just as good medium as high action yes?
Medium is a very subjective term...I have never seen adjustments posted by Low, Medium and High.
IMHO, action will have no effect on note sustain until you either experience uneven frets and/or action too close to a fret, or pickup, which interferes with the string's vibration.
Here's the settings I use most frequietly. Use it as a guide only.
Neck Relief: Set at .015" to .020"
Low E Action @ 12th fret unfretted: .050" to .060"
High e action @12th fret unfretted: .035" to .040"
1st fret string height unfretted: .020"
Then, when fretted at first fret, I like to see a minimum of .010" at the second fret, as shown:
Also, on humbuckers, I set the pole pieces to 4/32" from the strings, fretted at the last fret.
On single coils, you need a lot more distance to avoid Wolftones.
Also, I walk up every string, in 4 fret movements, listening for any anomalies. I also bend every string, at every fret, listening for choked-off notes, buzzing, etc.
RVA is a much more competent Luthier and I am in hopes he will chime in as well...