Pre HT question

Hi to all,
I like to keep my hair low around # 1/2 guard that’s a bit more lower than the 1# guard. Is it ok to get a haircut before the HT? what’s the best number clipper guard for the sides and top of the hair that will make it easier for doctor to do the HT? Since my HT is going to be a small session, around 350 to 400 FUE I imagine it will be less visible than larger session but will it be less visible enough for me to get a low fade without the gaps being visible. For those that don’t know whats a fade is the following pic is a fade. P.S. that’s not me on the pic
Thanks in advance.