jeff has answered all your questions, i dont have much to add, but.....my first piece was an all french lace....all after have been swiss...none are from this site though...
i am pretty sure you are referring to DiDi in NYC...the reviews have been mixed...but for the most part what i have gathered concerning her is...she'll get the job done...she is not friendly...isnt open to criticism if you are not happy and like most of the so called "pro's" she will get it on your head and it'll be passable...but nobody will be as meticulous as you.

for my 1st unit i actually drove up to Maine to get an in person cut in with debbie at split ends...she is great...friendly, willing to answer questions, will share her knowledge and really knows how to cut hair!

of course driving from staten island to maine for cut ins is not sustainable long term....i now just send out my piece with pics and detailed tweaks and she does a remote cut in...i also send pics of how short i wear my bio hair, which i do myself...when i get it back i do a bit blending with a blending/razor comb that i got from her....

my bio hair is done as follows to give you an idea of how short i go.....the first bottom inch to inch an a half (meaning just above my ears and all around the bottom) is buzzed with a tight #3 or if i use my adjustable clipper its a looser #2....above that for approx the same width i use a tight #4 (or looser #3 if using the adjustable). keep in mind that even with the longer guard i run it from the already clipped bottom up to where i stop. this is so there arent lines created and its a smooth transition.. last i use the longest guard which is tight #5 or again if using the adjustable a looser #4 and once again its run through all that was already clipped up to the edges of my bio hair...

hope that makes sense to ya....when you have it that short it is important to have the piece line up nearly perfect there is very little room for misplacement because there really isnt any length to hide errors...hope this helps